Long story short:
I've created a document in Microsoft Word 2010 and saved it as PDF. With the .pdf open now in Acrobat Reader 9.4.1 I have enabled the protection over the .pdf file by only allowing Printing and saved the protected .pdf. All of these actions are made on Windows 7 machine. Now when trying to open the protected .pdf on Mac (with Snow Leopard 10.6.6 and Preview) the .pdf opened only shows the lines and bullets but not the text.
Why is the text not visible in the protected PDF opened on Mac?
(is this bug or a "feature"?)
Note: the protected .pdf looks good on Windows 7 and it works on Mac if the .pdf has no protection.
A. What application are you using to add the protection? Reader cannot add any file security and I don't think the PDF feature of Word will either.
B. Mac Preview has issues with PDF standards so there may be some features that you will experience issues with that have no workarounds.
C. Have you checked the file after adding security to see if all fonts are embedded?