Rebecca:

It doesn't exist but I would love to see an option that forces that attachment of a document to a transaction, not only during manual cheque processing but in an invoice batch as well. Hopefully Softrak can consider this for s future release as well.

There is a way to attach missing documents from posted transactions, but they will only stay in AP whereas when attached to the unposted transaction the document will be passed to Ledger as well.

Open the applicable vendor profile and select the Transaction tab. Find the transaction and click on it to select. Now use the paperclip to attach documents to that transaction.