dh_fixperms makes all files in usr/share/doc in the package build directory (excluding files in the examples/ directory) be mode 644. It also changes the permissions of all man pages to mode 644. It removes group and other write permission from all files. It removes execute permissions from any libraries, headers, Perl modules, or desktop files that have it set. It makes all files in the standard bin and sbin directories, usr/games/ and etc/init.d executable (since v4). Finally, it removes the setuid and setgid bits from all files in the package.
When the Rules-Requires-Root field has the (effective) value of binary-targets, dh_fixperms will also reset the ownership of all paths to ``root:root''.