Probably the browser blocks new windows from popping up (window.open() function)

If you want to get around this: When the PDF is ready, give the user something to click on (a button or dialog) and call the window.open() from the onClick callback.

These errors are save to ignore. You have to wait some seconds until compiling has completed.

Note that the browser might prevent the website from opening the PDF (Pop-up blocking)

Yup, had to wait a bit, then enable popups from GitHub [Iceweasel 10.0.12, Debian Wheezy].

Would a download button appearing when the pdf has compiled be harder to do?

Nice demo

Aha okay. You might want to clean that up anyway. :)

OOOOooh.