Combine supported files in Acrobat 10 Pro fails for password protected files

I use Acrobat 10 Pro and wanted to combine a number of pdf-files to one big file.

It failed because the files in question have a permission password.

After I bought Acrobat on first creation of a pdf-file I was asked set a password

for reading and/or modifying it.

I decided to set no password for reading, but one for modification namely

<christian-name>.<surname> . I noted this down.

When I got the error indication after I tried to combine some pdf-files I tried

to remove the permission password. I was asked my password, but the program

refuses to take it.

What can i do, except to scan all the invoved pdf-documents once again, this time

without any password. It's quite a lot of them.

Thanks in advance.

Michael