QUESTION: Why do users sometimes have problems when trying to use Adobe Illustrator to edit a PDF file?
ANSWER: The short answer to this question is this: Adobe Illustrator is not and was never meant to be a general-purpose PDF-editing tool.
A document called the Adobe PDF Reference describes the format and structure of the code within a PDF file. This document, which was authored by Adobe Systems Incorporated, describes many different kinds of code that can be contained in a PDF file. The main reason you can't use Adobe Illustrator to edit just any PDF file is that Adobe Illustrator understands only a small subset of the kinds of code that are described in the Adobe PDF Reference.
You can run into trouble if you try to use Adobe Illustrator to edit text in a PDF file if that text uses fonts that aren't installed on the computer that's being used to do the editing — even if those fonts are embedded in the PDF file.
In general, you should be able to use Adobe Illustrator to edit a PDF file if the following things are true:
- The PDF file was created from within Adobe Illustrator by clicking File > Save As and choosing Adobe PDF (*.PDF) for "Save as type."
- The fonts used in the PDF file are installed on the computer that's being used to do the editing
You might be able to edit PDF files that were created by applications other than Adobe Illustrator, but — as stated above — this is by no means a sure thing, and you should not be surprised if it doesn't work.