You can sign a PDF on a Mac for free, with nothing to install. Open the file in Preview, show the Markup toolbar, choose Sign, create your signature and drag it onto the line. If you would rather not use Preview, or the file needs other work first, you can also sign in your browser without uploading the document.
This guide covers both routes, step by step. It also covers a question that matters in Singapore: when is a signature you place yourself enough, and when does the other party need something stronger?
TL;DR
- Preview signs PDFs on every Mac. Use the Markup toolbar, then Sign, then pick the Trackpad, Camera or iPhone/iPad method.
- The camera and iPhone methods usually give a cleaner signature than drawing on a trackpad.
- Finish all edits first (merge, compress, reorder), then sign, then save a separate copy and reopen it to check the placement.
- A placed signature image suits routine forms and approvals. Some Singapore workflows require a Secure Electronic Signature, such as Sign with Singpass.
- If you want to sign in your browser without uploading the file, FlowPDF's Sign PDF tool does it locally, with no signup and no watermark.
Table of Contents
- Sign a PDF in Preview, step by step
- Trackpad, camera or iPhone: which signature method works best
- Place the signature so it holds up
- Keep your saved signature private
- When a signature image is enough in Singapore
- Sign in your browser without uploading the file
- Our view: sign last, keep it local
- A short workflow for multi-document jobs
- Common problems and fixes
- FAQ
- Sources
Sign a PDF in Preview, step by step
Preview is the default PDF viewer on macOS, so this is the fastest route. The steps below follow Apple's Preview guide.
- Open the PDF in Preview. If another app opens it by default, right-click the file, choose Open With, then Preview.
- Show the Markup toolbar. Click the Markup button (the pen tip in a circle) in the toolbar.
- Click the Sign button. It looks like a signature on a line.
- Create a signature. Choose Trackpad, Camera or iPhone/iPad (details in the next section).
- Click your signature to place it. It appears on the page as an object.
- Drag it into position and resize it. Use the handles at the corners to match the signature line.
- Save a new copy. Use File, then Export as PDF, or Duplicate first, so the original stays untouched.
Once you have saved a signature, it appears in the Sign menu. Next time you only need steps 1, 2, 3 and 5.
If the PDF is a fillable form
Apple says that when a PDF has fillable fields, you can click a field and type. If the file is not an editable form, those fields will not respond. In that case add text with Preview's markup tools, then insert your signature. We cover this in more detail in our guide to filling a PDF form on a Mac.
Trackpad, camera or iPhone: which signature method works best
Preview offers three ways to capture a signature. Each suits a different situation.
| Method | How it works | Best for | Watch out for |
|---|---|---|---|
| Trackpad | Draw with a finger, press any key, then select Done | A quick signature when nothing else is at hand | Often shaky and hard to match your real signature |
| Camera | Sign on white paper and hold it up to the Mac's camera | A signature that looks like your pen signature | Paper must be level with the on-screen guide, and you may need to recapture |
| iPhone or iPad | Draw with a finger or Apple Pencil on a nearby device | A controlled, natural stroke without paper | Needs a nearby iPhone or iPad |
Apple notes that on a Force Touch trackpad you can press harder for a heavier line. The Camera method captures a signature written on paper, and the iPhone/iPad method accepts a finger or Apple Pencil, all per the same Apple guide.
Tips for a cleaner camera signature
- Use plain white paper and a dark pen with a medium tip.
- Sign in good light, without shadows across the paper.
- Keep the paper level with the guide line on screen.
- If the preview looks ragged, recapture. Do not accept a poor result because it is faster.
Place the signature so it holds up
A signature that lands in the wrong place or covers printed text can cause a form to be sent back. Take 30 seconds to check it.
- Zoom in on the signature line. Make sure the signature sits on the line, not over the name or date.
- Match the scale. A signature that is far larger than the surrounding text looks odd and can obscure content.
- Check the page. On a long contract, confirm you signed the page that asks for it, and every page that asks for initials.
- Check orientation. If a scanned page is sideways, fix that first. Our guide to rotating PDFs on a Mac shows how.
Do your edits before you sign
If you need to merge several files, remove pages, split a long document or shrink it for email, do that first. Sign the final version last. Changing the document after signing can undermine the version you meant to approve.
For those steps you can use FlowPDF's merge tool, split tool or compress tool. All of them run in your browser, so the files stay on your Mac.
Save a separate copy and reopen it
After placing the signature, save or export a new PDF. Keep the unsigned original as it is. Then close the file, reopen the new copy, and look at every page that you signed. Apple's workflow treats the signature as an object you position and resize, so a visual check is the only way to confirm it ended up where you intended.
Keep your saved signature private
Your saved signature is reusable personal data. Apple says Preview can make signatures available across your Macs through iCloud Drive, and that you can delete a saved signature when you no longer want it, as the Preview guide explains.
Two habits help:
- Do not create or store a signature on a shared or borrowed Mac, such as a library, office or school computer.
- If you sell or hand over your Mac, delete saved signatures first.
When a signature image is enough in Singapore
Most everyday paperwork does not need special tools. A rental viewing form, a school permission slip, an internal approval or a quotation acknowledgement is usually fine with a visible signature on a PDF.
The law does not reject a signature simply because it is electronic. The Singapore Government's developer guidance on e-signatures explains that Section 8 of the Electronic Transactions Act 2010 recognizes a method that identifies the person and shows their intention, as long as the method is reliable for the purpose or can be proven to have done those things. For background on how electronic signatures are treated more broadly, this guide to electronic signature validity is a useful read.
Ordinary versus Secure Electronic Signatures
The same Government guidance separates two categories:
- Ordinary Electronic Signature (OES): a practical method that shows who signed and that they meant to sign. A signature placed in Preview is of this kind.
- Secure Electronic Signature (SES): a stronger category. Under the Electronic Transactions Act 2010, a secure signature must be uniquely linked to and capable of identifying the signer, remain under the signer's sole control, and be linked to the record so that changes invalidate it.
Both can be legally valid. The difference is who carries the burden if a signature is disputed. With an SES, the guidance says the other party must prove tampering, while with an OES the burden works the other way. That is why SES is reserved for higher-risk or higher-value transactions.
Check the recipient's requirement first
Before you sign, ask the recipient what they accept. A bank, an agency or a counterparty's legal team may specify the signing method. If they require an SES, a picture of your handwriting in Preview will not meet it, however neat it looks.
In Singapore, one option for that is Sign with Singpass. Its documentation says signatures made through it are regarded as Secure Electronic Signatures under the Electronic Transactions Act 2010. The Government's product overview describes it as letting Singpass users sign remotely with the Singpass app, with each signature cryptographically linked to the signer.
For a high-value contract, a property transaction or anything regulated, speak to your lawyer or the receiving organization about which signature type they need. We do not offer certificate-backed digital signatures, and this guide does not replace legal advice.
Sign in your browser without uploading the file
Preview is great when you are on your own Mac. There are cases where a browser tool is more convenient:
- You are on a Mac that is not yours and do not want to install anything.
- You need to sign, merge and compress in one session.
- You want to keep the document off a third-party server.
FlowPDF's Sign PDF tool works in your browser, and the file is processed locally on your device. There is no upload, no account and no watermark, and it costs nothing. It runs in any browser on a Mac, so you can use it alongside Preview rather than instead of it.
If you want to understand the OES and SES distinction from a browser-signing angle, read our piece on signing PDFs in your browser in Singapore. If you are looking for Adobe alternatives more broadly, see signing locally without Adobe.
Preview or FlowPDF: a quick comparison
| Preview | FlowPDF in your browser | |
|---|---|---|
| Cost | Free, built into macOS | Free |
| Install | None | None |
| Signup | None | None |
| Where the file goes | Stays on your Mac | Processed locally, not uploaded |
| Works on shared or non-Mac devices | Mac only | Any device with a browser |
| Edit, merge, split and compress in the same place | Limited | Yes, in the same toolkit |
Both give you an ordinary electronic signature. Neither is a certificate-backed digital signature.
Our view: sign last, keep it local
We build FlowPDF around one idea: a document you are about to sign is often a private one. Contracts, tenancy agreements, employment letters and forms with NRIC details do not need to travel to a server to get a signature on them.
That is why we keep all processing in your browser. It is also why we advise signing as the last step. Most signing problems we see described are not about the signature at all. They come from a document that changed afterward, a signature placed over text, or the wrong version sent out.
Our practical routine:
- Keep the original untouched.
- Prepare the final document (merge, trim, rotate, compress).
- Sign once.
- Save as a new file and reopen it.
- Send only the signed copy.
We are also clear about limits. A placed signature is the right tool for routine approvals. If the other party needs identity-verified signing, use the method they ask for, such as Sign with Singpass, and do not try to stretch a simple signature to cover it.
— Ronald Ang
A short workflow for multi-document jobs
Students submitting forms, freelancers sending contracts and small businesses sending a pack of documents often have more than one file. A routine that avoids mistakes:
- Collect the files and merge them into one PDF if the recipient wants a single document.
- Remove pages you do not need and rotate any sideways scans.
- Compress the file if email limits are a concern.
- Open the final file in Preview, or in the browser tool, and sign.
- Export a new copy, reopen it, and check each signed page.
- Send it, and keep the unsigned original in your records.
You can find the whole set of tools on the FlowPDF tools page.
Common problems and fixes
- The Sign button is missing or greyed out. Make sure the Markup toolbar is showing, and that the PDF is open in Preview and not in a browser's built-in viewer.
- The signature looks jagged. Redo it with the Camera or iPhone method rather than the trackpad.
- The signature is too big or small. Select it and drag a corner handle.
- You cannot click into the form. The PDF is probably not an editable form. Add text with the markup tools instead.
- The recipient says the signature is not accepted. Ask whether they require a Secure Electronic Signature or a specific e-sign platform.
- You want to remove a saved signature. Delete it from the Sign menu in Preview, as Apple's guide describes.
FAQ
Can I sign PDFs on my Mac for free?
Yes. Preview is built into macOS and includes a signature tool, so you do not need Acrobat or any paid app. You can also use a free browser tool such as FlowPDF, which does not require signup or add a watermark.
How do I make an electronic signature on my Mac?
Open the PDF in Preview, show the Markup toolbar and click Sign. Then create your signature with the trackpad, the Mac's camera or a nearby iPhone or iPad. Click the saved signature to place it, then drag and resize it on the signature line.
Is a signature added in Preview legally valid in Singapore?
It can be. Under Section 8 of the Electronic Transactions Act 2010, an electronic method can satisfy a signature requirement if it identifies the person, shows intent and is reliable for the purpose. Some transactions call for a Secure Electronic Signature, so check the recipient's requirement. For high-value contracts, ask a lawyer.
Is it safe to store my signature on my Mac?
It is safe on a Mac that only you use, but treat it as personal data. Preview can sync signatures across your Macs through iCloud Drive, and you can delete a saved signature at any time. Avoid saving one on a shared computer.
Should I sign before or after compressing or merging a PDF?
After. Finish merging, editing, compressing and rearranging first, then sign the final file. Changes made after signing can undermine the version you meant to approve.
Sources
- Fill out and sign PDF forms in Preview on Mac, Apple Support
- E-Signatures, Singapore Government Developer Portal
- Electronic Transactions Act 2010, Singapore Statutes Online
- Overview of Sign, Sign with Singpass
- Sign with Singpass, Singapore Government Developer Portal