Invoices move between people: supplier to accounts payable, contractor to client, clinic to insurer. They travel as scans or phone photos of paper, each 2-8MB at 300dpi, and they hit a hard wall fast — most mail servers reject attachments over 25MB, portals cap single files around 5MB, and accounting platforms often cap per-document size. A folder of twelve scanned invoices is easily 60MB and simply will not go through. Invoice images are mostly white space and text, the best possible candidate for compression: keep the scan at a legible resolution, compress it, and the document stays fully readable at a fraction of the size. Do not compress so hard the invoice number or bank details blur. Compress on quality, check one page at full zoom, then run the batch.