Is the file upload size available in the admin interface - I can't seems to find it…
R
You mean to change it? Yes – System Configuration --> Global Preferences will change it on a system-wide basis. You can also change it on the Preferences screen for a User Group.
Remember, you may need to change php.ini if you want to increase this value.
Also mind apache config settings for max post size (httpd.conf). I think it's set at 8mb by default - you need to make sure php, apache and matrix are all on the same page if you want to say, upload a 16mb file.