pdf security set to allow printing but did not allow printing on 2 out of 13 docs

i have a security protection policy in Adobe X pro and part of the policy is set to allow high resolution printing.  I sent out 13 documents all with the same security policy.  Two recipients were unable to print the documents and when i went to in to check my saved pdf it said the password was wrong.  It is strange because all the other documents were fine.  As the policy is saved and applied by just clicking it i don't understand how this has happened.  it is to do with the password currupting?  Or could it be something with the recipients system?  i have re-saved the document to pdf and applied the saved policy and it works fine but the original document still does not accept the policy.

any ideas would be gratefully received

Thank you

Cat