Hello, I am testing your form. is it possible to let my clients charge files bigger than 1Mb? Up to 10 Mb could be fine.

Yes, you can allow for file uploads that are larger than 1MB. Please take a look at the following guide:

http://www.jotform.com/help/33-Changing-the-Upload-Size-Limit

Please let us know if you need any further assistance, we are here to help.