How to sign a PDF on Mac — with Preview, and when not to
To sign a PDF on a Mac, use Preview's Sign tool. When your Mac has no trackpad or camera, or is not yours to save a signature on, open Sign PDF in a browser tab instead.
Signing a PDF is the one desktop-PDF job a Mac genuinely built in well. Preview, the app that already opens the file, has a real signature tool, and for most people on their own Mac it is the right answer — no download, no account. This is the honest version: how Preview does it, the two specific cases where it gets in the way, and the browser route for those.
How do I insert my signature on a Mac?
Open the PDF in Preview, click the Markup toolbar button (the pen-tip icon near the top right), then the Sign button. Preview creates a signature three ways: draw on the trackpad, hold a signed piece of paper up to the camera, or sign on a paired iPhone or iPad. Click the saved signature to drop it in, drag it into place, and press Command-S.
That covers most people. When one of the two cases below applies, Sign PDF does the same job in a browser tab — Safari or Chrome, whichever you already have open.
Open the tool
Open Sign PDF. It is an ordinary web page — nothing to install and no account to make.
Choose the PDF
Click the upload area and pick the file. Every page is rendered on your Mac first, so a long document takes a moment before the signature pad appears.
Draw or type your name
Draw on the pad in black or blue ink, or switch to Type and enter your name to have it set in a script face. The preview shows exactly what will be placed.
Confirm it
Click Use signature. It is trimmed to its own edges, so the empty space around your name does not become empty space around the placed image.
Place it and apply
Drag the signature onto the line, resize it from a corner handle, then click Apply signature. The signed copy downloads with _signed on the end of the name.
How do I sign a PDF on a Mac without a trackpad?
Draw it with your mouse. Preview can only create a signature from a trackpad, a camera, or a paired iPhone, so a Mac mini or an iMac with a plain mouse and no camera has none of the three — which is why signing a PDF on a Mac without a trackpad is such a common search. Sign PDF's pad takes the mouse directly: press and drag to draw a line, and a single click leaves a dot.
It reads pointer input rather than touch specifically, so the same pad works with a mouse on a desktop Mac, a trackpad on a laptop, or a finger on a touchscreen — the drawing code does not care which one is moving the cursor.
Is it safe to sign a PDF on a shared or work Mac?
Yes, if you use a tool that keeps nothing. Preview saves every signature you create into its own signature list, held on that Mac and synced through iCloud Keychain, so it is ready next time — handy on your own machine, awkward on a borrowed, lab, or locked-down work one. Sign PDF stores nothing: your signature lives only as an image held in the open tab.
That is not a reassurance, it is how the page is built. The signature is a small image kept in memory while you position it; loading a different file clears it, closing the tab discards it, and there is no signature library, no file written to disk, and no server to send it to. Nothing is left behind on a Mac that is not yours.
Is this the same as a digital signature?
No. Both Preview and this add a picture of your signature to the page. A digital signature is a cryptographic certificate bound to the document's exact bytes — it proves who signed and exposes any change made afterwards, which no draw-on-the-page tool produces. For a form, a delivery note or an internal sign-off a drawn mark has always been enough; for a contract a court might read, use a qualified e-signature service. Drawn, typed, digital: three kinds of PDF signature sorts out which is which.
If you type your name rather than draw it, a Mac renders it in Bradley Hand — the tool asks for Segoe Script first, which is Windows-only, so a Mac falls through to the next face it does have installed. And each pass places one signature on one page: a contract needing initials on three pages is three rounds of sign, place and download, worth knowing before you start rather than at page two.
All of it runs on the Mac in front of you, in the browser you already have open. How to sign a PDF is the full desktop walkthrough with the placement details; signing on an iPhone and on Android cover the phones, and if the document has real form fields to complete as well, Fill PDF Forms handles those first.
