Highlighting PDF Viewer

Highlighting PDF Viewer is based on Mozilla's PDF.js project as "a general-purpose, web standards-based platform for parsing and rendering PDFs".

Our viewer extension receives highlighting meta-data from the server and marks keywords in PDF viewer. In addition, it includes additional features, as well as workarounds for some PDF.js issues (e.g. printing and text copy).

Highlighting PDF Viewer can be used as a drop-in replacement for PDF.js viewer, with advanced search capabilities:

  • If the viewer URL specifies search terms using the "#search=" fragment, the search will be handled using Highlighter's internal search engine.
  • The original Find bar in the viewer is replaced with the Power Search.

Power Search

Power Search

Power Search bar allows user to find any text in the PDF using advanced search capabilities powered by Highlighter Server, including:

  • Search for individual terms or phrases (Boolean search)
  • Proximity search
  • Wildcards
  • Stemming
  • Fuzzy search

Check live example here.

Highlighter in PDF Viewer

Use of Highlighting PDF Viewer has numerous advantages over burning highlights into PDF:

  • Hit-to-hit navigation within the document is available.
  • Users access the original PDF documents and can benefit from web browser caching.
  • It's a web based PDF viewer compatible with major web browsers and mobile devices. No client-side PDF viewer installation is needed.
  • It brings a unified user experience across platforms.
  • Highlighting process is faster and more lightweight than burning-in highlights.

Highlighting PDF Viewer is installed as a part of Highlighter Server and is automatically referenced in results.

The viewer requires a modern web browser. It's not compatible with Internet Explorer 9 and doesn't run with IE Compatibility Mode enabled. In addition, IE has slower JavaScript engine resulting in low performance when document pages contain high resolution images (scans).


By default, for IE 9 and older, PDF Highlighter delivers results as burnt PDF instead in the viewer.


Highlighting PDF Viewer is a part of Highlighter distribution, and there is no need for a separate download.

If you don't use Highlighting Server but would like to use the improvements that we made to PDF.js viewer, you can download it here and use it absolutely free.