I have had trouble with pdf's created with pdfcreator where I include a specific TrueType font (VanDijk to name it). The pdf file, when opened, just has boxes instead of the text. If I save as a PDF/A or PDF/X, I get an error message when I try to open the pdf in Adobe Reader that it "cannot find or create the font..."
The error seemed at first to crop up with an upgrade of pdfcreator (I think it was from 0.9.9 to 1.0.0) but a later version seemed to sort it out. But then I found that if I used pdfcreator on some PC's, the problem was there, and on other's it wasn't no matter what version I was using. More recently, I seem to always have the problem.
If I create the file with another pdf writer (eg I have tried Bullzip and also the internal QuickBooks pdf writer) I don't have the problem.