Do you want to know what’s annoyed me most about recently switching from Google Chrome to Firefox (or, more precisely, its 64-bit variant, Waterfox)? The lack of a built-in PDF viewer, that’s what.

In Chrome, you’d click on a PDF link, and it would open in Chrome: do the same in Firefox, and it would save the PDF to disc instead. Incredibly annoying. The development of a built-in PDF previewer was welcome news to my ears, but having appeared in Firefox 15 Beta, it disappeared from the final version. The good news is that it’s there, and you can switch it on. If you know how.

If – like me – you’re desperate to view PDFs in your Firefox (or Pale Moon, or Waterfox) browser window, but you don’t want to use a third-party plug-in such as Adobe Reader, then this is what you need to do.

View PDFs inline in Waterfox and Firefox with our tip.

First, make sure you using the latest version of Firefox or Waterfox – download Firefox 15 FINAL here, Waterfox 15.0 here, and Pale Moon 15.0 here (or here if you want the 64-bit version).

Next, open the Firefox (or Waterfox or Pale Moon) menu and choose Add-ons. Select Plugins and see if Adobe Acrobat is present. If it is, select it and click its Disable button.

Now, open a new tab and type about:config into the Address bar, clicking I’ll be careful, I promise! if it appears. Type browser.preferences.inContent into the Search box and hit [Enter]. When it appears in the Preference Name list, check its Value: if it’s set to ‘false’, double-click it to change it to ‘true’.

Now type pdfjs.disabled into the Search box and hit [Enter]. This time, the default value is ‘true’, so double-click it to change the value to ‘false’.

Pale Moon users need to also switch the built-in PDF viewer on – type pdfjs.firstRun into the Search box, press [Enter] and double-click it so its value reads ‘true’.

There’s one final check to perform: open the Firefox, Waterfox or Pale Moon menu again, but this time choose Options > Options, then switch to the Applications tab. Check the Portable Document Format (PDF) setting – if it’s not set to “Preview in Firefox/Waterfox/Pale Moon” then click the current setting and choose Preview in Firefox/Waterfox/Pale Moon to complete the switch.

Once done, you should now find clicking on PDFs in your browser opens them in a new tab (you can test your new settings by opening this step-by-step guide to installing Windows XP by yours truly), complete with navigation controls and the all-important download button in the top right-hand corner of the window.