Problems with Illustrator CS font substitution

[Jessica_M_Theodor@adobeforums.com]

I have a PDF that was created by a Windows user, using fonts that I don't have on my Mac, that I need to edit. I want to change the fonts using Find Font. This works fine in AI 10, I can open the file, run Find Font and change the fonts to the OpenType versions of those fonts. This works as it should, text that was originally in Souvenir Light is correctly changed to ITC Souvenir Std Light, Italic to the correct Italic version, etc.
However, since I need to edit the file to insert glyphs of foreign accents, I would like to do this using AI CS, but when I open the file in AI CS instead of 10, the font substitutions are all off - things that were italic in the original are not, and vice versa, and I have to go and manually change them all, because Find Font won't work because the original fonts have been messed up.

Has anyone else seen this behavior, or have any way to fix it? The workaround of editing first in AI 10 and then opening in AI CS to add glyphs is time consuming and I would like to be able to do this in one version of Illustrator.
Thanks.

[William_Chang_Jr.@adobeforums.com]

I have a similar problem. On Illustrator 10 documents created on my old OS 9 machine, I used Helvetica bold and Helvetica oblique. However, if I try to open them in Illustrator CS on my OS X 10.3 machine, the font substitutions mess everything up, despite the fact that I do have Helvetica on my OS X 10.3 machine, and documents created in Illustrator CS [and MS Word] using Helvtica bold and italics works fine. Any help in getting my old Illustrator documents to open in Illustrator CS without messing up the fonts would be greatly appreeciated. Thanks!