How to sign a PDF in Adobe Acrobat Reader (and when it isn't enough)

Adobe Acrobat Reader, the most widely used free PDF reader, includes a signing tool called "Fill & Sign". It lets you put your signature on a document in a minute. What it doesn't do is request a signature from someone else or record who signed.

1. Open the PDF in Acrobat Reader. 2. Find the "Fill & Sign" tool (in the tools pane or the right-hand menu). 3. Click "Sign" → "Add signature". 4. Type your name, draw your signature with the mouse or upload an image. 5. Click where the signature goes and adjust the size. 6. Save the PDF.

If you upload an image, make it a PNG with a transparent background: a white background will cover the document's line.

The Adobe Acrobat Reader app for Android and iPhone has the same option: open the PDF, tap the pen icon or "Fill & Sign", create your signature with your finger and place it. Then share it by email or WhatsApp.

That tool places an image of your signature on the PDF. It doesn't verify your identity, doesn't record the date or the device, and doesn't help your client sign: you'd have to send them the file, wait for them to sign it themselves and send it back.

For an internal document that's fine. For a client contract, a lease or a payment agreement, you want something that leaves a record.

Electronic signature platforms solve exactly that: you upload the PDF once, mark where each person signs and they get a link. They sign from their phone without installing Adobe or anything else, and the final PDF includes a certificate showing who signed, when and from where.

Firmiu's free plan lets you send 3 documents a month with up to 5 signers each, and the completed PDF can later be opened in Adobe Reader, which flags on its own if anyone modified it after signing.