Add Attachment

I try to add attach file to PDF document using this way:

.....
        PTFileSpec *fileSpec = [PTFileSpec Create:[doc GetSDFDoc] path:tempSignDataFile embed:YES];
            
            PTFilter *ptFilter = [fileSpec GetFileData];
            
            [doc AddFileAttachment:@"attach00" embedded_file:fileSpec];

....

after save PDF ope with Acrobat PDF Reader in the attachments list I can see my file but with 0 size.

"tempSignDataFile" exists!!!

Why?

Thanks in advance