This content originally appeared on HackerNoon and was authored by Iron Software
\ Let's open with the conclusion, because that's the most useful thing we can do for you: PdfPig is good. We mean that without qualification, and we'll spend most of this article showing you why.
That probably sounds odd coming from a team that ships a commercial PDF library. We're the developer community at Iron Software, and yes, we make IronPDF, which competes in the broader .NET PDF space. So treat this as a peer-to-peer review with a transparent bias, not a neutral one. The reason we wanted to write this PdfPig review is that the .NET open-source PDF ecosystem has a lot of libraries that overpromise and underdeliver, and PdfPig is genuinely not one of them. Credit where it's due makes the rest of our reviews mean something.
Here's the thesis in one sentence: PdfPig is honest about its scope, and that honesty is the most underrated feature in any open-source library. The catch (and there is one) is that the scope is narrower than it looks at first glance, so the real question isn't "is it good?" It's "does its scope match what you actually need to do?"
To make that concrete before we go further, here is the entire setup ceremony for reading a PDF with PdfPig:
using UglyToad.PdfPig;
using PdfDocument document = PdfDocument.Open("report.pdf");
Console.WriteLine($"Pages: {document.NumberOfPages}");
Reading a PDF Document with PDFPig C
Two lines of using-directives, one to open, one to query. No factories, no DI registration, no async setup, no native binary to ship alongside. That minimalism is part of why we want to write about it honestly, it's a refreshing contrast to a lot of what's in the .NET PDF space.
What PdfPig Is, In Plain Terms
PdfPig is a .NET port of Apache PDFBox, the long-standing Java PDF library. It's licensed Apache 2.0: permissive, no copyleft, safe for commercial products without legal ambiguity (which, if we're being honest, is the bar a lot of "free" .NET PDF libraries quietly fail to clear). The package on NuGet has over 21 million downloads and a healthy community of contributors. Stars on the GitHub repository sit around 2,400, with active issue triage and a maintainer who actually merges PRs.
That last point matters more than star counts. We've seen plenty of OSS libraries with 10x the stars and zero recent commits. PdfPig's most recent push at the time of this writing was late April 2026, meaning the maintainer was active on the repo within the last two weeks. Releases over the last 18 months: v0.1.11 (July 2025), v0.1.12 (November 2025), v0.1.13 (December 2025), and the current stable v0.1.14 (March 2026). That's a roughly quarterly cadence, which is plenty for a library focused on a stable problem domain.
One real caveat on versioning before we go further: PdfPig is pre-1.0. The README is upfront about this: minor versions can change the public API without SemVer guarantees until 1.0 is reached. If you're pinning a dependency in production, pin the patch version, not just the minor. The README's API-stability warning is worth taking literally.
The Core API Reference: Extracting Text Like It's 2026
Let’s get to code, because that’s why you’re here. Here’s the simplest possible thing PdfPig does well: extracting text from a PDF while also exposing low-level data for analysis, including letter positions, bounding boxes, and font metadata:
using UglyToad.PdfPig;
using UglyToad.PdfPig.DocumentLayoutAnalysis.TextExtractor;
using PdfDocument document = PdfDocument.Open("invoice.pdf");
foreach (Page page in document.GetPages())
{
string text = ContentOrderTextExtractor.GetText(page);
Console.WriteLine($"Page {page.Number}: {text.Length} chars");
}
A few details matter here. ContentOrderTextExtractor.GetText(page) is not doing OCR, and it’s not inventing structure that the file doesn’t contain. It walks what the PDF stores and rebuilds a text view from that.
That distinction is why PdfPig is useful. You can start with a plain string, then drop down into letters, words, and layout analysis when the output needs more control.
If you use page.Text instead, treat it as a convenience view of the page’s content stream order rather than human reading order. That can be fine for quick checks, but it’s not what you want if you care about columns, headers, or mixed-position content.
When extraction gets messy, confirm the exact behavior and supported analysis types in the API reference.
Output
That's it. Open a document, iterate pages, get text. No service registration, no factory pattern, no fluent builder you have to learn. The class names are honest about what they do: ContentOrderTextExtractor extracts text in content order, NearestNeighbourWordExtractor extracts words by spatial proximity. There's a small set of layout-analysis tools and they each do one thing.
A gotcha that caught us off guard the first time: page.Text is not the property you want. It returns the raw content stream order, which is rarely the human reading order. The README is explicit about this: "you should not use page.Text directly, unless you know what you're doing." We've seen developers use it anyway because it's the obvious property name, then spend an afternoon wondering why their extracted invoice totals are showing up before the line items. Use the layout-analysis extractors instead. They exist for exactly this reason.
Going Deeper: Document Layout Analysis with Words, Letters, Bounding Boxes
This is where PdfPig earns its place in our toolbelt. Most “extract text” libraries give you a string and call it a day. PdfPig gives you a tree: pages, then letters with positions, then words assembled by spatial algorithms, then text blocks via page segmenters, then optional reading-order detection, with access to text content, letter positions, and PDF coordinates on the page.
Here’s what that looks like for a richer extraction:
using UglyToad.PdfPig;
using UglyToad.PdfPig.DocumentLayoutAnalysis.PageSegmenter;
using UglyToad.PdfPig.DocumentLayoutAnalysis.ReadingOrderDetector;
using UglyToad.PdfPig.DocumentLayoutAnalysis.WordExtractor;
using PdfDocument document = PdfDocument.Open("statement.pdf");
Page page = document.GetPage(1);
IReadOnlyList< Letter> letters = page.Letters;
var wordExtractor = NearestNeighbourWordExtractor.Instance;
IEnumerable< Word> words = wordExtractor.GetWords(letters);
var pageSegmenter = DocstrumBoundingBoxes.Instance;
IReadOnlyList< TextBlock> blocks = pageSegmenter.GetBlocks(words);
var readingOrder = UnsupervisedReadingOrderDetector.Instance;
IEnumerable< TextBlock> ordered = readingOrder.Get(blocks);
foreach (TextBlock block in ordered)
{
Console.WriteLine($"[{block.BoundingBox}] {block.Text}");
}
That layered model matters when you need geometric reasoning instead of plain text scraping. It also helps when inspecting page contents and rebuilding document layout analysis workflows.
Docstrum is the obvious example here, but recursive xy cut and nearest neighbour algorithms are part of the same family of layout-analysis approaches rather than one-off tricks. Because PdfPig targets .NET and stays close to the PDF object model, this kind of deep access extends into the PDF document’s internal structure.
Near the end of a pipeline, that extra reach is useful too: PdfPig can read document metadata, PDF metadata, interactive form fields, and annotations when those matter to analysis.
It can also extract internal graphics, images, embedded files, and hyperlinks from a PDF document.
Console Output
If you've ever tried to do invoice parsing or statement parsing, you already know that "give us all the text" is the easy half of the problem. The hard half is "give us the text grouped by visual region, in the order a human would read it." PdfPig hands you the building blocks for that, including bounding box coordinates you can reason about geometrically. The Docstrum algorithm and the unsupervised reading-order detector aren't perfect, but they're real implementations of real research, not heuristics duct-taped together. These tools are well-suited to line-item extraction on supplier invoices and tabular data from multi-column PDF reports, exactly the kinds of workflows where regex-over-flat-string approaches collapse.
One more thing worth flagging in this PdfPig review: encrypted PDFs work fine if you have the password: pass it as the second argument to PdfDocument.Open. We've watched teams switch libraries because they assumed encrypted reading would be a paid feature. With PdfPig, it isn't.
Worth knowing on the runtime side: the current stable PdfPig package targets .NET Standard 2.0 and .NET Framework 4.6.2, which means it runs across current .NET LTS releases (.NET 8 and .NET 10), older Framework apps, and anything in between. The same API surfaces in mixed environments without target-framework friction.
The Creation Footnote — and Why We're Calling It a Footnote
PdfPig can create PDFs through PdfDocumentBuilder, but with clear limits. The README has an example: register a Standard 14 font, and with TrueType fonts supported when fonts are registered with PdfDocumentBuilder prior to use, add a page, drop some text, write bytes, and even track the page number as you build. It works for what it’s documented to do.
But the documentation itself is upfront about what it can’t do, and these matter for production workflows. From the README:
Document creation supports very limited changes to existing PDF documents. However it does not support any of the following: Editing forms, Copying or changing annotations, metadata or document structure data, Adding or removing text with existing fonts.
Advanced manipulation tasks like redaction or adding watermarks are not supported and usually need another library. That’s not a backhanded criticism, it’s the maintainer being honest about what the creation API is for. It’s there so you can produce simple debug PDFs (the wiki shows an example of overlaying bounding boxes on an extracted page for layout-analysis debugging, which is a great use case for this API). It’s not there to be your invoice generator, your report builder, or your form-filling pipeline.
If your workflow is “read PDFs and extract data,” PdfPig is excellent. If your workflow is “read PDFs, transform them, fill forms, sign them, and emit new PDFs,” you’re going to hit the wall on the creation side fast, so teams that need to create PDFs from richer inputs usually pair it with another tool.
Where PdfPig Stops
We want to be careful here, because the goal isn’t to list everything PdfPig doesn’t do. That’s an unfair frame for any library. The goal is to map the boundary so you know whether your workflow lives inside it or outside it. It works on PDF files, but it is not meant for converting HTML or converting from other document formats into the PDF format.
What PdfPig genuinely does not do, per its own documentation:
- HTML-to-PDF conversion. Not its job. The wiki recommends other libraries for this.
- PDF rendering to images. Not its job either, which also means it does not support generating images from PDF pages. The wiki points at docnet or PDFtoImage. There’s a separate PdfPig.Rendering.Skia package that adds rendering, but it’s a separate concern.
- Form population. Forms are readable but read-only: you cannot change values or add new form fields.
- You need to digitally sign PDFs for compliance, contracts, or audit trail purposes: No signing, no signature validation in the way a compliance-driven workflow would need it.
- PDF/A or PDF/UA compliance. Out of scope.
- Editing existing PDFs. You can read them; the creation API can produce simple new pages but isn’t intended for round-trip editing of arbitrary input PDFs.
- Accessibility tagging. Out of scope.
Scanned images and OCR-heavy workflows are outside PdfPig’s scope and typically need a separate OCR tool. Support gaps around document formats are intentional scope boundaries, not defects in a PDF-reading library.
None of these are flaws. They’re scope boundaries the maintainer drew on purpose, and the documentation tells you exactly where they are. That’s the rare, valuable thing.
When PdfPig Is the Right Tool for .NET Core
Concretely, here are workflows where we'd reach for PdfPig first:
- Data extraction from PDFs. Invoices, statements, regulatory filings, scientific papers, anything where the PDF is the input and structured data is the output. PdfPig's letter-level positioning and word/block extractors are specifically designed for this.
- Search indexing. Pulling text out of a PDF corpus to feed into a search engine. The text-extraction APIs are fast and stable.
- Layout analysis and document understanding. Research workflows where you need bounding boxes, reading order, and the geometric structure of the page. PdfPig is one of the few .NET options that exposes this layer.
- Lightweight inspection tooling. Debug viewers, validators, content audits. The basic creation API is good enough for overlays and annotations on extracted content.
If your job description includes the phrase "we need to read a PDF and pull data out of it," PdfPig should be on your shortlist before you look at anything paid.
When PdfPig Leaves You Short
The flip side, also concretely — and if you need broad read/write/manipulation coverage, commercial libraries may be a better fit:
- You need to render HTML or web content to PDF: PdfPig isn’t your tool. You need a browser-engine-backed library or a layout engine.
- You need to fill in PDF forms and save them back: PdfPig can read the form fields, but it can’t write them.
- You need to digitally sign PDFs for compliance, contracts, or audit trail purposes: out of scope.
- You need PDF/A archival format compliance for regulated industries: out of scope.
- You need to generate complex multi-page reports with tables, charts, and styled typography from a template: the basic creation API isn’t built for this.
- You need to round-trip-edit existing PDFs (read in, modify, write out): The creation API explicitly doesn’t support this for non-trivial documents.
Teams may also compare copyleft alternatives as a licensing consideration alongside commercial options.
For workflows that span both reading and writing — extract data from a PDF, generate a new PDF based on what you extracted, sign it, archive it — you’ll need either a second library to handle the write half or a single library that covers both halves.
A Complementary Approach
This is where we think the honest framing matters most. PdfPig and a generation-capable library like IronPDF aren’t strictly competitors; they’re often complementary. We’ve seen teams pair them: PdfPig for the extraction half of a workflow, a generation library for the rendering, signing, and form-filling half. This split approach gives one library deep access to a PDF document while another handles output workflows.
A toy version of that pattern:
// Stage 1: PdfPig extracts data from the source document
using UglyToad.PdfPig;
using UglyToad.PdfPig.DocumentLayoutAnalysis.TextExtractor;
string sourceText;
using (PdfDocument source = PdfDocument.Open("incoming-invoice.pdf"))
{
var page = source.GetPage(1);
sourceText = ContentOrderTextExtractor.GetText(page);
}
InvoiceData parsed = ParseInvoice(sourceText);
// Stage 2: A generation-capable library produces the audit PDF
// (IronPDF, QuestPDF, or another generation library would handle this stage)
string auditHtml = $"< h1>Audit for {parsed.InvoiceNumber}< /h1>...";
// ... HTML-to-PDF conversion, signing, etc., happens here
You don’t have to use IronPDF for the second stage, QuestPDF is another option. The point is that “PdfPig vs anything else” is often the wrong frame. PdfPig can access internal structure details during extraction from the source file, while a second library handles writing or conversion. PdfPig is the right tool for its half of the workflow. The architecture question is what tool covers the other half, and whether you want one library that does both halves or two libraries each doing what they do best.
Final Honest Take
This is the part of a PdfPig review where the marketing instinct is to pivot to a sales pitch. We're going to resist that. If you're building data-extraction tooling and PdfPig fits your workflow, use PdfPig. The library is well-maintained, fairly licensed, technically solid, and refreshingly honest about its scope. We'd rather you use the right tool than the one we make.
If your workflow needs both reading and writing capabilities and you want to evaluate unified options, the IronPDF documentation is a reasonable place to look, and so is the QuestPDF documentation, read the licensing carefully on whatever you pick. The honest answer to "which library should we use?" almost always depends on your specific workflow, your team's constraints, and your budget. We'd rather give you the framing than the conclusion.
The reason we wrote this isn't to praise an "OSS competitor." It's that the .NET PDF space has too many libraries claiming to do everything and quietly failing at half of it, and PdfPig is the opposite, it claims to do a focused set of things, and it does them. That's worth saying out loud.
Need to Complete Stage 2 of Your Pipeline?
PdfPig is world-class at extraction, but if your application needs to handle the second half of the document lifecycle—generating audit trails, rendering HTML reports, filling forms, or applying digital signatures—consider testing IronPDF.
You can easily pair PdfPig’s extraction logic with IronPDF’s high-velocity generation engine inside a single production service.
- No HTML Restrictions: Convert complex, modern HTML5, CSS3, and JavaScript layouts into PDFs instantly.
- Compliance Ready: Native support for cryptographic digital signatures, form field flattening, and strict PDF/A or PDF/UA archival formats.
👉 Get a Fully Functional IronPDF Free Trial and start building the write-side of your pipeline today.
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:::info Disclaimer: This article is paid content. HackerNoon’s editorial team has reviewed it for clarity and quality standards, but the views, claims, benchmarks, and comparisons expressed are solely those of the sponsor, and HackerNoon assumes no responsibility for third-party assertions contained in sponsored content.
:::
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This content originally appeared on HackerNoon and was authored by Iron Software
Iron Software | Sciencx (2026-06-10T15:00:49+00:00) PdfPig C# Review: A Focused Open-Source PDF Library in 2026. Retrieved from https://www.scien.cx/2026/06/10/pdfpig-c-review-a-focused-open-source-pdf-library-in-2026/
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