Yes a distinct improvement. What I would suggest initially is to make this as a component override - could you do this ? I would test out and produce some examples, document and so on. The size parametersmight need to be max-size type or percentages which we could experiment with.
Adding in the pdfjs viewer as part of the jD install would obviously be a good idea and simplify matters. But as present we are working very much on the next major release of jD (called v3.9) so in my opinion that would be the best time to include the viewer in the jD installation. - and make the facility a feature?
Users might want to just show a section of the pdf so is it a possiblility to specify the number of pages or even better the page range? At this time it looks like 4 or 5 parameters in the Back End would be needed for inclusion in the jD config.xml file, probably the Specials section.First "Do you wish to use embedded pdf viewer?" with a Yes/No selection The Yes would then reveal the pages and size parameters.
I would suggest a suitable place to load the viewer file would be in a new directory in the components/com_jdownloads/assets called say pdfjs although perhaps it could go into the existing js directory.
What do you think?Colin