As discussed here:
CustomPress includes custom field types which are very useful, one of which is the upload field. However, if you upload anything other than an image using this field (such as a PDF or zip file) there’s no easy way to retrieve the file or provide a link to it.
The OP in the link above found a way to retrieve the attachment using the ID of the custom field for a post, but this is pretty fiddly. It would be great to see some enhancements to CustomPress to support non-image files through the upload field, such as providing a method of retrieving the URL via the embed codes, possibly from a new property?