Is this in a browser form or a filler form? qRules will let you save out file attachments to a SharePoint library, so they aren't in the form XML, but that first involves attaching the file to the form. If the form is a filler form, I'd add a browse button and write some code to browse for the current file location and then copy the file to the desired location and set a field's value to the new location so people can find it.