iText Suite 9.5: Supporting Both Brotli Compression and Quantum Safe Signatures!

In this iText Suite release from Apryse, the focus is on adding support for two upcoming additions to the PDF specification: Brotli compression and post‑quantum digital signature algorithms.

Open‑source libraries like iText serve a critical role in keeping the PDF ecosystem modern, interoperable, and future‑proof. By introducing early support for these new technologies, we can not just help to popularize them, but our implementation can also serve as an example for others in the community.

Support for Brotli Compressed PDF Streams

Compression technology has advanced significantly since the general-purpose Deflate/Flate compression was introduced in PDF 1.2. The Brotli compression algorithm is a more modern compression algorithm that builds on similar principles as Deflate, with some key improvements. While it was originally developed to reduce the size of fonts transmitted over the Internet, it can also be applied to the same wide variety of use cases as Deflate, while typically achieving better compression ratios.

Decompression of Brotli streams is supported out-of-the-box in iText Core. However, as Brotli compression will soon be part of the PDF specification, iText Core needs to support not just reading Brotli-compressed PDF streams, but also writing them. Therefore, we’re pleased to introduce the new brotli-compressor module to enable this functionality.

Because Brotli support is not yet standardized and is not widely implemented across current PDF processors, the module is only available from our artifactory, and so should be used cautiously until formal standardization and broader ecosystem support arrives.

One of the iText Core development team has written an article for the PDF Association if you'd like to learn more about iText's implementation of Brotli compression.

Post-Quantum-Safe Digital Signature Algorithm Support

While quantum computing is still in its early stages, it creates a real long‑term security concern known as “harvest now, decrypt later.” In this scenario, attackers collect encrypted data today and store it until a future quantum computer becomes powerful enough to break the encryption.

As a precaution, cryptography experts have been developing post-quantum cryptography (PQC) algorithms designed to resist both classical and quantum attacks. Similarly, the PDF industry is taking proactive steps to ensure digitally signed PDF documents are safe from these risks. At the PDF Association’s PDF Days 2025 event, an agreement to integrate quantum-resistant signatures into the PDF specification was reached. Among the post-quantum cryptographic standard approved by NIST are two digital signature algorithms: ML-DSA (Module-Lattice-based Digital Signature Algorithm) and SLH-DSA (Stateless Hash-based Digital Signature Algorithm).

Since official support for these algorithms will soon be added to the PDF specification, you can rest assured that iText is fully prepared for these developments. As such, iText Core 9.5.0 includes a proof-of-concept implementation for both the creation and validation of post-quantum digital signatures in PDFs. We’re committed to evolving this proof of concept into fully robust, standards‑compliant support as soon as the PDF specification is finalized. With the quantum threat approaching, iText ensures you’re building on a platform prepared for the future.

Enhanced PAdES Signature Profile Validation

Our goal of making the task of digitally signing and validating PDF documents with iText easier continues with enhancements to preset PAdES signature profiles. The PAdES profile validation is improved and can detect when the Document Security Store (DSS) changes between revisions, improving timestamp validation accuracy.

In addition, to build on the support for the EU List of Trusted Lists (LOTL) from previous iText Core releases, we've added new samples for the Ukraine and Moldova trusted lists.

Bug Fixes and Miscellaneous Improvements

For iText Core we have introduced a common, cross‑platform JSON AST and converters to serialize/deserialize between Java/C# objects and a unified JSON representation, improving maintainability and GraalVM/AOT support. We also added support for East Asian (Japanese) line‑breaking rules in iText Core's layout module, improving typography for Japanese text by avoiding orphan punctuation at the beginning of lines.

We also resolved a number of both customer and internally reported bugs, covering form filling and flattening, XRef calculations in large documents, OCG layers in append mode, metadata handling in encrypted documents, and the use of OCSP/CRL responses in non-timestamped revisions.

As always, we have updated the iText Core add-on modules available in the iText Suite. For full details on the changes, refer to the release notes for Core and the add-ons on the iText Knowledge Base.

RUPS 26.01

The latest version of the RUPS (Reading and Updating PDF Syntax) PDF diagnostic tool is also now available. RUPS is extremely handy for PDF debugging purposes, and this latest version introduces Brotli compression support, and the ability to manipulate stream filters.

In addition, to add to the support for ASN.1 data structure for digital signature objects from the previous release, this version adds support for the ISO/TS 32004 MAC extensions, along with a number of bug fixes and quality-of-life improvements.

Showcase PDF

As always, we’ve made the iText Core release notes into a showcase PDF document. Not only does it conform to the latest PDF/UA-2 standard for accessible PDF documents, as well as the PDF/A-4F archiving standard, it’s also digitally signed.

But that’s not all, as we’ve created a public repository where you can find an example .NET project to automatically generate accessible PDF documents from suitable web pages, applying the correct fonts, injecting custom content, generating a table of contents, and more.

You can find full details of what’s new in iText Suite 9.5 in the release announcement. Alternatively, check the release notes on the iText Knowledge Base for more technical information, download links and related documentation/examples.