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PDFs Don't Display Properly In Firefox 19

A PDF displayed in a Mozilla Firefox window may not display properly. Symptoms include:

  • The display looks like a scanned image rather than with crisp text;

  • Black or grey strips.

This may occur when using Firefox 19, which introduces its own PDF viewer.

To disable the Firefox 19 viewer:

  1. Open Firefox.

  2. Under ToolsOptions, choose Advanced.

  3. Next to Adobe Acrobat Document, choose Use Adobe Reader:

  4. Click OK.

In later versions of Firefox (approximately 40 or greater):

  1. Click the settings icon:

  2. Under Options, Applications click Portable Document Format (PDF) and select Use Adobe Acrobat.


  1. Open Firefox.

  2. In the address bar, enter about:config.

  3. Click I'll be careful, I promise!

  4. Search for pdfjs.

  5. Double-click the line which reads pdfjs.disabled until Status is “user set” and Value is “true”.

To undo, repeat the steps but double-click so Status is “default”.

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