Document assembly not allowed

I have created several PDF forms using Adobe Designer 7.0 for Windows XP and I want to compile them into a single PDF document using Adobe Acrobat Professional 7.0's "Create PDF from multiple files" option. But when I try, I get a message that "The file (name) is protected. It cannot be used for this command" for each file in turn. When I open the files individually and look at the security settings, I see "Document Assembly: Not Allowed". I was wondering how I could change the settings to allow document assembly. Acrobat Help just tells me to contact the original document author...but I *am* the original document author!