Tag

Internals

11 posts

PDF Compression Filters Explained

A PDF is full of compressed content: page streams, embedded images, fonts, embedded files. The compression schemes are called "filters" in PDF terminology. They

Guides Internals

May 19, 2026·8 min read

PDF Incremental Updates Explained

When you save a PDF after editing, the writer can either rewrite the whole file or append a small update at the end. The second option, called an incremental up

Guides Internals

May 18, 2026·7 min read

Digital Signature Internals in PDF

A digital signature on a PDF is more than a scribbled image. It's a cryptographic operation that proves who signed, when, and that the document hasn't been alte

Security & Privacy Signing Internals

May 17, 2026·8 min read

PDF Attachments and Embedded Files

A PDF can carry other files inside it. The feature, called "file attachments" or "embedded files," has been in the PDF spec for two decades and powers everythin

Guides Internals

May 16, 2026·7 min read

XFA Forms Explained

XFA XML Forms Architecture is the more powerful, more complex, and increasingly deprecated form technology in the PDF ecosystem. XFA forms support dynamic layou

Forms Fillable Forms Internals

May 15, 2026·7 min read

Embedded Video and Rich Media in PDFs

A PDF can contain video, audio, and other rich media. Hover over a still image in a marketing PDF and it plays a product demo; open a research paper and a 30sec

Guides Internals

May 14, 2026·7 min read

3D PDFs Explained

A PDF can contain a fully interactive 3D model: a CAD assembly, a molecular structure, a building model, a medical scan. Open the PDF, click the 3D area, and yo

Guides Internals

May 13, 2026·7 min read

Interactive PDFs With JavaScript

PDFs can run JavaScript. The feature has been in the spec for decades and powers everything from form validation to interactive scientific charts to malicious p

Guides Internals

May 12, 2026·7 min read

PDF Internals: Objects and Streams

A PDF looks like a single document, but inside it is a small structured database of objects. Open a PDF in a hex editor or a text editor and you see a soup of o

Guides Internals

May 11, 2026·8 min read

Multimodal LLMs and PDF Documents

The shift from textonly LLMs to multimodal models text plus vision has reshaped what AI can do with PDFs. A 2023 LLM had to depend on text extraction; if the ex

AI AI Internals

Apr 9, 2026·8 min read

Building a RAG System With PDF Knowledge Bases

Retrievalaugmented generation RAG is the dominant pattern for getting an LLM to answer questions over your own documents. PDFs are the most common source format

AI AI Internals

Apr 1, 2026·8 min read