• Welcome to PDF4QT

    I would like to introduce new software for processing PDF documents. Why start a new project from scratch when we already have poppler or ghostscript, and also popular viewers such as Evince or Okular? All of these are good, but are quite old and lack many functionalities compared to commercial solutions.


  • Introduction to plug-ins

    PDF4QT Viewer Profi uses plug-ins to provide additional features to users. There are currently seven plug-ins, which the user can turn on/off in the Options dialog. They are turned off by default.

  • How to annotate/markup a PDF document

    PDF4QT ViewerProfi offers extensive annotation tools. You can annotate a PDF document with geometric shapes, sticky notes, stamps, text boxes and various forms of text highlighting. The tools are very easy to use, using your mouse to create annotations directly in the page of a PDF document. Go to the ‘Insert’ menu to start annotating your document. Annotator creates annotations...

  • Encrypting a PDF document with a strong encryption algorithm or decrypting it

    When you want to protect a sensitive PDF document from unauthorized access, you may want to encrypt it using a strong encryption algorithm. Standard PDF 2.0 offers two ways to encrypt a PDF document. The first is password protection, the second certificate protection. PDF4QT supports the first option by utilizing strong AES-256 encryption, or for backward compatibility, RC4 and AES-128...




  • Upcoming feature: Adjusting Colors for Visually Impaired Persons

    For individuals with visual impairments, the ability to adjust colors on a digital document can greatly enhance readability. Standard color schemes often lack the necessary contrast and can strain the eyes, making it difficult for visually impaired users to engage with the content.

  • Upcoming feature: Create Bitonal Document from Scanned Pages

    In the digital era, handling large scanned documents, especially from old books, poses challenges. This article introduces a new feature in my software that addresses this issue. It allows the conversion of color images in these PDFs into bitonal or black-and-white format, significantly reducing file size. The feature also offers customization options during the conversion process, giving users control over...