Since an encoded file is an ASCII file, you can edit it to change the access permissions and file label. The first line of an encoded file might be:
begin 600 pictures.tar.Z
The number 600 defines the access permissions for the original file - which the decoded file will also have. This is followed by the file_label to be used as the filename (pictures.tar.Z) for the decoded file.
To change the access permissions edit the number 600 to something more appropriate such as 644 and then save the file. You can change the file label in the same way. For example:
begin 644 from_mike.tar.Z
The decoded file will now have the name from_mike.tar.Z and everyone will be able to read it.