How to increase performance of docman?

cascading style sheets

For start, docman uses cascading style sheet which is located at distribution directory html/docman.css. If it's left there, docman.php will serve it using docman.css?STYLE=CSS. However, if you move it to Apache DocumentRoot ( see directory layout) if will get it from here (and enable browsers and/or proxies to cache it).
You can enable it using ln -s as described in installation instructions.

Trustees

Trustees are compiled on-the-fly into php code and store in file on disk until next change of trustee file. Since it's just included in most times, it's a great save our of time, but it would benefit anyway from some kind of PHP acceleration (like Zend Optimizer or APC).