If you want to upload a CV to send it to a contact and you get an error, it could be that the CV document is too large.
The maximum of the request body (the request sent to the webserver) is 8.388.608 (8MB). The request body contains more then the attachment (e.g. cookies and other headers). This means that the maximum of the attachment is actually lower. This depends also on the codes given.
It is not possible to change this restriction.