Update pdftex URL to fix issue #3

[waldyrious]

Fixes issue #3.

(Note: I'm submitting this on behalf of @tajpulo, who made a commit with the change in their fork, but for some reason didn't create an associated PR in this repo. Their authorship of the commit is fully preserved, and they —unlike me— retain the ability to make changes to this PR's branch; that said, I'd be happy to close this PR in deference to another one created by them, if that is preferred.)

[tajpulo]

You are right. I must have missed it. Thank you very much for your efforts!