A family of Microsoft word processing software products for creating web, email, and print documents.
Yes it could be printer driver, but since it is happening for both physical printer and PDF printer, I suspect it may be a font substitution issue.
If one of the computers does not have the exact same font used in the document, then Word will "substitute" another font that is on the computer. If you are lucky, the substitution is close so there are minimal changes. Sometimes the substitution is really bad.
**Font Substitution Problems**
http://wordribbon.tips.net/T007836_Font_Substitution_Problems.html
When your document uses fonts that are not available on your computer system, Word substitutes other fonts that it feels are close to what the document calls for. This can cause problems, as outlined in this tip.
**Finding Word’s Font Substitutes**
http://wordribbon.tips.net/T012657_Finding_Words_Font_Substitutes.html
Different machines can have different fonts installed on them. Because of this, it is possible for a document that looks fine on one machine to look entirely different on another, if that other machine doesn’t have the same fonts installed. When this occurs, Word substitutes fonts of its choosing for the missing fonts. Here’s how to discover what Word is doing behind the scenes.