I believe DSD's InstaDocs would do that but it is a bit overkill for just that. However, you may find it has enough value for your other modules as well.

If you want to dabble with a script, you could always create a folder accessible to all users to hold the documents and use a script to create a sub folder by PO number, Receipt No, or Invoice No then use a simple button script to launch the folder so the user can copy the doc into the folder. Then you can use another simple button script added to whichever inquiry tasks to want to utilize it from that will either open the folder or open a matching doc if it is named correctly. 

If you use the script to open the matching doc, you may not need the sub folders, you could just have all the docs dumped into a single folder but they would need to be properly named so the script can reference and open them based on information from the current record.

If a receipt memo is added to a Receipt of Invoice Entry that memo WILL flow through to A/P Invoice History.