I've added 2 new options pertaining to AMS Comment Attachments.
The first option allows you to control the max file size (KB) pertaining to comment attachments. Default value for this is set to 2048 KB.
The 2nd option allows you to control with file extensions are allowed. Default values for this are the five image extensions as shown below
Here you can see that by adding the extension 'pdf' to the option "Allow comment attachment file extensions", I am allowed to upload a pdf file to an AMS comment (attachment displays use core XF macros, the same macros that posts use).