limit

sudo vi /etc/trac/trac.ini

Updated the attachment max size line to this:

[attachment]
max_size = 5242880

This made it 5 MB (I just multiplied their number of bytes, which equaled 250Kb, by 20).

Reference

http://trac.edgewall.org/wiki/0.11/TracIni

Upping PHP's maximum file size upload limit:

Your problem: the file upload settings page on your Drupal site (if you've found it) is telling you silly PHP won't let people upload big files, to wit:

Your PHP settings limit the maximum file size per upload to 2 MB.

There's two places that this has to change in your php.ini file; this can also be set in your settings.php PHP initialization variables.