I noticed some strange effects when including existing pdf graphics in my laTeX documents:
Most file work flawlessly, but some PDFs that were created on a different machine (or from the web) cause the whole page on which they are embedded to become ever-so-slightly distorted. I only notice the difference in a side-by-side comparison, but once you see it, it’s obvious. The text layout seems slightly broken, and when you zoom in you can see it better.
I will try to make some screenshots to further elaborate, but in the meantime:
Has anyone seen this before and how can I get rid of these distortions?
I had one case where a similar effect showed up, but it disappeared when printing.
Almost certainly, Mica is right, and this is a PDF viewer problem.
A guess: if the problem is with lettering (distorted or missing letters and symbols), this could be a problem with non-embedded fonts, where your PDF viewer is making bad substitutions for the fonts in the document. The first place to look is at the list of fonts in the document, then at what your viewer will look for to use when it renders the document. It could be that you have fonts that your PDF viewer isn’t finding.