I've been PC based for 9 years now. This is the first time I've had a major conversion issue. I bought Crossfont, and that fixed it. (Not 100%; I still had to make some adjustments within the doc -- should have just bought the font!)
Jane, the Menu Maker
BTW -- Always looking for good freelancers!
To the best of my knowledge, Mac and Win PostScript and TrueType fonts are different and not cross platform compatible. OpenType fonts are truely cross platform. I hear that you can use Win TT fonts on a Mac, but not vice versa.
As I understand it, print service providers are reuired by the font EULA to own the font even though the customer provides it.
I suggest you ask your customer to purchase the modern OpenType versions of the fonts.
Here is the breakdown:
Windows can use OpenType, Windows Type1 and Windows TrueType fonts.
Windows cannot directly read Mac TrueType or Mac Type1 fonts.
Macintosh can use OpenType, Mac Type1, Mac TrueType, and Win TrueType.
Adobe products can read some Windows Type 1 fonts if installed in the correct folder.
I recommend TransType Pro from FontLab.com for converting fonts to OpenType (keeping in mind any legal issues from the font foundry). Better yet, switch to OpenType Pro fonts from Adobe.
Its 2015 now why doesn't any huge company like you guys create a format that carries both the PC and Mac font so this problem wont happen any longer. But then I blame Windows mostly because I'm budgeting for a Mac due to one of these problems. But then here is an idea for you, why don't Adobe create more space in Adobe files that carries the original fonts for both the PC and/or Mac font so if you receiving a file you wont have to download it first.