Sign a PDF on your Mac without uploading it
By Himanshu Ranjan · Updated 8 November 2026
To sign a PDF on a Mac with FileDial, select it in Finder, hold the right Option key and choose Sign & Lock › Place signature… It adds an image of your signature, not a certificate signature. Add initials to every page… handles contracts that need initials throughout, and Flatten forms locks filled fields into the page. A signed copy appears beside the original, and nothing is uploaded.
How to do it with FileDial
- Select the PDF in Finder and hold right ⌥.
- If it has form fields, choose Sign & Lock › Fill form… first.
- Choose Sign & Lock › Place signature… and position your signature.
- For initials throughout, choose Sign & Lock › Add initials to every page…
- Run Sign & Lock › Flatten forms on the signed copy before sending it.
Your original file stays untouched. The result is saved beside it, and every result has Undo.
Which option to pick
| Tool | Use it when |
|---|---|
| Place signature…Sign & Lock | Adding your handwritten-style signature as an image; it is not a certificate (digital ID) signature. |
| Add initials to every page…Sign & Lock | Contracts or leases that need initials on each page; saves a new copy beside the original. |
| Fill form…Sign & Lock | The PDF has fields to type into before signing; saves a new copy. |
| Flatten formsSign & Lock | Finalising: fields become plain page content so entries can't be casually edited. |
Image signatures, certificate signatures and what you actually need
There are two very different things called a PDF signature. An image signature is a picture of your handwriting placed on the page, the digital equivalent of signing a printout and scanning it. A certificate signature uses a digital ID to cryptographically seal the document and show whether it was changed afterwards. FileDial's Place signature… is the first kind, and its note says so plainly.
For most everyday paperwork, such as a lease, a consent form, a freelance agreement or a school permission slip, an image signature is what the other side expects. Some processes, typically certain government, legal or regulated workflows, require a certificate signature from a specific provider. If the instructions mention a digital ID or a signing certificate, use the method they specify.
Two habits make signed PDFs more robust. Fill every field before you sign, then flatten, so the entries become part of the page. And keep the unsigned original, which FileDial does automatically by saving the signed version as a new file.
Why not sign it on a website?
Documents that need signatures tend to carry personal details: addresses, salaries, bank details, identity numbers. Free signing and conversion sites collect all of that along with an image of your signature. Cybernews reported in July 2024 that two online PDF services left storage open and exposed 89,062 user-uploaded files, including contracts and IDs.
The FBI Denver Field Office warned in March 2025 that free online document tools can scrape personal data and return files carrying malware. FileDial signs on your Mac and works offline.
Other ways to sign a PDF on a Mac
Preview has a built-in signature tool. Open the PDF, show the Markup toolbar, click the Sign button and create a signature with the trackpad or by holding signed paper up to the camera. You can then place it on the page. It is free and works well for one document.
FileDial is quicker from Finder when you sign often, need initials on every page of a long contract, or want to fill, sign and flatten as separate steps with Undo on each. The signed copy sits beside the original, which stays unchanged.
Questions
Is a FileDial signature legally binding?
FileDial places an image signature, not a certificate signature. Whether that is accepted depends on the document and who receives it. If the instructions ask for a digital ID, use the method they specify.
Can I add initials to every page automatically?
Yes. Choose Sign & Lock › Add initials to every page… FileDial saves a new copy with your initials on each page, beside the original.
Should I flatten a PDF after signing?
It is a good habit for filled forms. Flatten forms turns fields into plain page content, so the entries can't be casually edited by the next person who opens it.
Does signing work offline?
Yes. Every tool runs on your Mac and works with Wi-Fi off. Neither your document nor your signature is uploaded, and file names and contents are never sent anywhere.
How much is FileDial?
There is a 1-day free trial with every tool, no card and no account. Then it is $20 once for a lifetime licence on 2 Macs, with a 14-day refund.