This PDF displays with question marks instead of letters

It might be that the fonts aren't being embedded into the PDF, that would cause them to not render correctly on a computer that did not have the fonts installed and Adobe Reader may be faking the look of fonts that it doesn't have. Open the PDF in Acrobat on your PC and in the "File" menu select "Properties..." and then click on the "Fonts" tab. Each font listed should have a remark like "Embedded" or "Embedded Subset".

If that is the case, you may have to change your PDF creation settings (not sure how you are creating the PDFs, so I'm no help there) to make sure that all fonts are embedded.

This is a Chrome bug. It has been marked fixed in version 27, so the easiest thing to do would be to wait for the upgrade or to upgrade now.

To fix the existing PDFs, you can do the following:

1. Open the PDF in Preview
2. File->Save

This will rewrite the PDF so that it does not have the issue.