Without an integration there is no specific need to approve documents. You can download a .csv file without approving. However, once approved, if Auto-Archive is turned on in company settings the invoices will move to the archive folder keeping the inbox clear of old invoices.
If Auto-Archive is turned off, invoices can be manually archived by selecting the required invoices using the checkbox on the left. Clicking on 'Actions' at the top of the page and selecting 'Archive'.