How to Reduce a PDF File Size for Email on iPhone

Most email providers cap attachments around 25MB, and it’s an easy limit to hit without realizing it. A PDF made from ten or fifteen photographed pages, common for scanned contracts, school forms, or a stack of receipts, can quietly balloon past that number. Gmail or Outlook won’t always explain why the send failed, it just sits there or bounces back. Grabio’s Compress PDF option fixes this from the iPhone share sheet in a couple of taps, free and on-device.

Why a Scanned PDF Blows Past Email Attachment Limits

A PDF built from photos of documents is really a stack of full-resolution images stitched together. One page might be fine, but a ten-page scan can easily land at 20 to 40MB. Most email apps cap outgoing attachments at 25MB (some cap smaller for incoming mail on the recipient’s side too), so a document that opens fine on your phone can fail silently the moment you hit send. There’s no built-in warning in iOS that tells you a PDF is too big before you try attaching it.

How to Reduce a PDF’s File Size on iPhone with Grabio

1. Add Grabio to your iPhone once, it’s a free Apple Shortcut. Get the free Shortcut here.
2. Open the PDF in Files or Mail and tap the Share button.
3. Scroll down the share sheet and tap Grabio.
4. Grabio detects it’s a PDF and opens the PDF menu, tap Compress PDF.
5. Pick where to save the smaller file in the Files save dialog, then Grabio shows “✓ Done, saved to Files.”
6. Go back to Mail, attach the compressed version instead of the original, and it should clear the size limit.

Is It Private and Free on iPhone?

Compression runs using Apple’s native optimizePDF action directly on your iPhone, nothing uploads anywhere, so it works even with no signal. Grabio is 100% free forever: no account, no login, no subscription, and no daily cap on how many PDFs you compress.

Reduce PDF File Size for Email: FAQ

How much smaller does a PDF get after compressing?

It depends on the source. A scan built from full-resolution camera photos often drops by 60 to 80 percent, since that’s where most of the bloat lives. A PDF that’s already mostly text sees a smaller reduction because there isn’t much image data to shrink.

Will the recipient notice a quality drop?

Compression optimizes the embedded images and file structure, it doesn’t rasterize or strip the text layer, so a scanned page stays legible and any selectable text stays selectable.

What if the compressed file is still too big?

Very heavy multi-page scans sometimes need a second pass, or you can split the PDF into two emails. If the file was built from your own photos in the first place, compressing each photo before you build the PDF also helps.

Related on iPhone: compress a PDF for upload limits, merge PDF files, or PDF & Document Tools.