Add PDF Reciept to existing expenses

I wait to upload my receipt until it comes through in my card so I don't have duplicates. Since there is no way to manually combine expenses. When the charge comes through you can only take a picture or upload, neither let you upload a PDF. If you upload a PDF separately then you have duplicates and it doesn't normally catch them. I would like to just attach a PDF to a already submitted expense OR be able to manually combine duplicates.