Send a signed PDF back the right way: the 2-minute checklist

Flatten or check the file here

Flatten PDFForms and annotations into content. Free, runs on your device.Open

If you signed in the getPDF editor, you do not need this tool: the editor’s Save menu has Save flattened PDF. Use the tool above for a PDF you filled elsewhere. It runs on your device and nothing is uploaded.

The checklist

Tick them off as you go. Nothing here is stored; it is just for you.

• Flattened, if I am the last signer and the document has fields or marks
• Named so they find it: document, my name, signed
• Size under about 18 MB, or their limit if they gave one
• Same thread, with 1 line on what is attached and what happens next
• My copy kept, the editable one too, where I will find it in 3 years

Each point, with the reasons:

1. Flatten it, if you are the last to sign

The editor offers 2 saves. Save PDF keeps form fields as fields: “Fields, marks and notes stay editable in any app.” Save flattened PDF draws them into the page: “Filled fields and marks become part of the page, so nobody can change them.”

Pick the flattened one when 2 things are true: the document has form fields, highlights or notes, and nobody signs after you. Flattening stops a recipient’s viewer from showing your fields differently (or blank) and stops anyone retyping an answer.

If someone still signs after you, send the normal save, so they can fill their fields. Multiple signatures on one PDF has the order.

Your signature itself is not what flattening is about. A signature placed with getPDF is written into the page as drawn lines or a picture, so it shows the same in every viewer with either save. What flattening protects and what it does not is in what PDF flattening protects.

2. Name it like they will search for it

getPDF names its saves after the file you opened: lease.pdf comes back as lease-edited.pdf or lease-flattened.pdf. That is a start, not a name. Rename it to what it is, who signed and its state:

• lease-graz-jane-cooper-signed.pdf
• offer-letter-karol-michal-signed.pdf
• invoice-2026-114-approved.pdf

Never scan_final_2.pdf, never Document.pdf. The person receiving it has 30 others; a name they can search for is a courtesy that gets your document processed. In Chrome and Edge on a computer, the save dialog lets you type the name as you save; other browsers save to your downloads, where you rename it.

3. Check the size against their inbox

Signing barely changes a file’s size. In our tests a drawn signature added about 4 to 12 KB, a typed one about 11 KB and an uploaded 1,200 by 400 pixel signature picture about 60 to 100 KB. If your file is large, the reason is the document, usually photographed or scanned pages, not your signature.

The limits that matter (from our facts sheet, checked on 11 October 2026):

Mailbox	Limit	Largest file that fits, roughly
Gmail	25 MB per message	18 MB
Outlook.com	25 MB for the whole message	18 MB
Outlook app, internet accounts	20 MB by default	15 MB
Outlook app, Exchange accounts	10 MB by default	7 MB
Microsoft 365 work mailboxes	35 MB by default, set by the admin	26 MB
iCloud Mail	20 MB	15 MB

Attachments travel encoded, about a third bigger than the file, which is why the right-hand column is smaller. The receiver’s company server can be stricter than any of these, and a bounce from their side looks just like one from yours. The full list is in email attachment size limits.

Too big? Compress it first; it runs on your device too, and its result shows the size before and after. Compress the flattened copy, the one you send.

Compress PDFPresets or a size target, shows what changed. Free, runs on your device.Open

4. Reply in the same thread

Do not start a new email. Reply to the one the document came in, so the request, the document and your signed answer sit together with their dates. Write 1 line that says what is attached and what you expect next:

Hi Karol, the lease is attached, signed on page 12 and initialled on every page. Could you confirm you received it? Jane

Asking for a confirmation is worth the extra words: the reply is your record that they hold the same file you sent.

5. Keep your own copy

Keep 2 files in the folder where you keep contracts, not in your downloads:

• The signed copy you sent, exactly as attached. If a disagreement ever comes up, this is what you signed.
• The editable copy (the normal save), if you flattened. Flattening cannot be undone, and if the other side asks for a small correction before they countersign, this is the one you fix.

The email thread is a third copy, but mailboxes get cleaned out and accounts get closed. 3 years from now you want the file on your own disk.

When the document carries ID or bank numbers

Protect PDFAES-256 password and permissions. Free, runs on your device.Open

Email is not end-to-end encrypted by default: the message sits readable in both mailboxes, and between some mail servers it still travels without encryption on the way (Google’s Transparency Report tracks how much mail reaches Gmail encrypted). For a lease, an offer or an invoice approval, that is normal and fine. For a document with a passport number, a tax number or bank details:

1. Protect the PDF with a password before you attach it.
2. Send the password another way: a text message, a phone call, a messenger.
3. Never in the same email as the file.

How to do it well, and how strong the protection is, is in password-protect a PDF before emailing and send a confidential PDF by email.

The honest part

This checklist does not make a signature stronger. A drawn or typed signature is a simple electronic signature, fine for everyday documents; the email trail and your kept copy are what back it up. getPDF does not make certificate signatures and does not send documents for signature or track who opened them. If a recipient asks for those, they need a signing service or a qualified signature, not a better email.

A flattened PDF can still be edited by someone determined. Flattening stops casual changes and viewer quirks. Your kept copy is what shows a change, if one ever happens.

If the document was digitally signed by the other side, any tool that writes a new copy of it (compress, flatten) ends that signature’s validity, and getPDF warns you when that happens. Sign it in the editor with the normal Save PDF, which adds your changes after their signed version, and send that file without flattening or compressing it.

For the whole signing job before this step, start at Sign and fill a PDF.