User Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:43.0) Gecko/20100101 Firefox/43.0 Build ID: 20151221130713 Steps to reproduce: I've got two PDFs, both single pages holding a funny image. They were both created using Atalasoft's PDF product, using the exact same code path. Both are configured to be self printing. Both pass validation tests, and both appear to be exactly the same other than the images. I try to get them both to print by dragging them and dropping them onto the firefox browser. Actual results: One opens the print dialog, and the other reports "There was an unexpected problem while printing.", but then shows the PDF exactly as it should and allows the PDF to be printed. Expected results: They both should open the print dialog, and they both should be printable. Again, other than the image, they are exactly the same and were produced by the exact same tool in the exact same manner. What's going on here? Why is one failing while the other succeeds? FYI, the images contained are just meme pics. One is MJ sitting, looking sad, with the text "when you didn't take your phone to the bathroom because you thought you only had to pee", and the other is Mr Rodgers flipping the bird. Nothing NSFW or soul scarring. Unless Mr. Rodgers flipping the bird scars your soul.

Is the bug more likely to be in the pdf.js implementation?

There aren't any errors in the console except for the expected one. Here's what you get when you drop the broken PDF on the browser Unknown pseudo-class or pseudo-element 'selection'. Ruleset ignored due to bad selector. viewer.css:59:13 Unknown pseudo-class or pseudo-element 'fullscreen'. Ruleset ignored due to bad selector. viewer.css:151:21 Unknown pseudo-class or pseudo-element 'fullscreen'. Ruleset ignored due to bad selector. viewer.css:199:37 Unknown pseudo-class or pseudo-element 'fullscreen'. Ruleset ignored due to bad selector. viewer.css:214:21 Unknown pseudo-class or pseudo-element 'fullscreen'. Ruleset ignored due to bad selector. viewer.css:222:21 Unknown pseudo-class or pseudo-element 'selection'. Ruleset ignored due to bad selector. viewer.css:1356:2 PDF ec0b02753502daa4769a7f13a2446098 [1.4 DotImage PDF Encoder / Atalasoft, Inc.] (PDF.js: 1.1.469) viewer.js:6746:1 Warning: JavaScript is not supported CSS issues (who cares)debug info from the pdf and the standard warning about javascript not being supported. Please note that this warming is shown whenever a PDF has embedded javascript. There's a "hack" to check and see if the PDF is self printing, which checks the javascript for the print call using a regex and then calls window.print() if found. It's after window.print() that the error dialog is shown. I tried debugging it, but it's not in javascript (or not accessible in the release version?)

Already fixed in FF44.