PDF.js Express vs. PDFTron

PDF.js Express wraps a PDF Viewer around the PDF.js rendering engine to view, annotate, form fill and sign PDF documents. In comparison, PDFTron provides a commercial rendering engine that covers all platforms, provides 100+ features and is compatible with 30+ file types.

When to use PDF.js express:

When to use PDFTron:

  • UX needs to be a competitive differentiator where users expect fast, reliable & accurate rendering
  • Documents include the large and complex
  • Viewing more file types including MS Office, CAD and Images
  • Require wider feature set: editing, creation, extraction, archiving and more
  • Simplifying development across multiple platforms

Rendering Engine

PDF.js Express uses the PDF.js rendering engine, an open-source rendering engine built by Mozilla and supported by the open-source community.

PDFTron is a commercial rendering engine that was developed in 1998 and has been refined over the last 20 years. This PDF engine is more accurate, reliable and faster when rendering PDFs in a web browser. It is supported by PDFTron developers who can address rendering issues quickly.

Learn more: Guide to Evaluating PDF.js Rendering | PDF.js Reliability Benchmark

PDF.js Express (PDF.js open source)PDFTron (Commercial)

PDF Viewer

Multiple display modes (fit to page, fit to width, full screen)checkcheck
Page transitions (continuous, page by page)checkcheck
Layout (single, double, cover)checkcheck
See high-quality thumbnailscheckcheck
See document outline and bookmarkscheckcheck
Print documentscheckcheck
Full localization supportcheckcheck
View PDF layers (OCGs)check


Collaborate in real-timecheckcheck
Freehand, free text, shape, comment annotationscheckcheck
Stamp document with text, imagescheckcheck
Watermark to prevent distributioncheckcheck
User roles and permissions (control access to each annotation)checkcheck
Annotation events to trigger custom functionalitycheckcheck
Measurement toolscheckcheck
Create custom annotationscheckcheck
Snap to control points for increased precisioncheck
Ability to bake annotations into underlying PDF documentcheck

UI Customization

Fully responsive UIcheckcheck
Customizable UIcheckcheck
UI written in React.JScheckcheck
UI Source code downloadablecheckcheck
Dark Themecheckcheck
Hide/Show Download/Print and other toolscheckcheck
Create your own UIcheckcheck

PDF Forms

User form fillingcheckcheck
Merging form datacheckcheck
Programmatically prepopulate formscheckcheck
Extract forms data and save values separatelycheckcheck
JavaScript field validation/formattingcheckcheck
Customize form appearancecheckcheck
Set fields to read onlycheckcheck


Sign by using hand-drawn annotationcheckcheck
Save signatures for signing multiple pagescheckcheck
Signature form field supportcheck
Create digital signaturescheck
Certify PDF documentscheck
Extract signatures for validationcheck


Multiple search optionscheckcheck
Ambient string, return context to your searchcheckcheck


Rendering engine

Open-source community

1-on-1 support

PDF Viewer

1-on-1 support

1-on-1 support

Document Conversion

File Conversion?Enable support for viewing using WebViewer Server for viewing BMP, WMF, EMF, GIF, JPG, JP2, JPC, PNG, TIF, HTML, TXT.check
Office to PDF Conversion?Enable support for viewing DOCX, XLSX, PPTX and/or using WebViewer Server for viewing DOC, DOCX, XLS, XLSX, PPT, PPTX, RTF, ODT, ODS, ODPcheck
CAD Conversion?Enable support for viewing with WebViewer Server: DWG, DXF, DGN, RVTcheck

Additional Features

Content Extraction(11)chevron_rightcheck
Document Creation(12)chevron_rightcheck
Page Manipulation(11)chevron_rightcheck
Optimizer?Optimizes PDF documents by reducing the file size, removing redundant information, and compressing data streams using the latest in image compression technology.check
Flattener?Can be used to speed-up PDF rendering on mobile devices and on the Web by simplifying page content (e.g. flattening complex graphics into images) while maintaining vector text whenever possible.check
Redaction?Offers options to remove (not just covering or obscuring) content within a region of PDFinfocheck
PDF/A?Convert generic PDF’s to PDF/A (ISO 19005-1)check
Document Compare(2)chevron_rightcheck
PDF layers (OCGs)(3)chevron_rightcheck
Colour Separation(3)chevron_rightcheck
Low-level Document Editing (4)chevron_rightcheck
Content Replacer?Replace images and text inside of your templatescheck
Advanced Image Rendering(4)chevron_rightcheck


Learn more

With PDF.js Express you can easily add out-of-the-box features to your PDF viewer

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