For software manuals and other documentation, it is important to use a license permitting free redistribution and updating, so that when a free program is changed, the documentation can be updated as well.
On the other hand, for small supporting files, short manuals (under 300 lines long) and rough documentation (README files, INSTALL files, etc.), the full FDL would be overkill. They can use a simple all-permissive license.
Here is a sample text for such an all-permissive license. This is just the license text itself. For a complete sample document, see the previous sections.
Copyright @copyright{} 2016 Free Software Foundation, Inc.
Copying and distribution of this file, with or without modification,
are permitted in any medium without royalty provided the copyright
notice and this notice are preserved.