How to sign a PDF on Windows, Mac, iPhone, or Android

Choose the kind of signature first

The fastest method depends on what the recipient means by “sign.” A visible electronic signature is a typed name, drawing, or signature image placed on the page. A certificate-backed digital signature also provides cryptographic information about the certificate and later document changes. A managed signing service can add identity checks, delivery records, timestamps, and an audit trail.

Ask the recipient which kind they require before editing the file. A school form or routine acknowledgement may accept a visible mark. A regulated filing, property transaction, financial authorization, or document that names a specific signing platform may not.

FileGizmo adds a visible signature. It does not verify identity, issue a certificate, lock later edits, or create a legal audit trail. Built-in Preview and basic Reader signing controls have similar limits when used only to place a visible mark.

The best starting option on each device

Device	Practical first choice	Why it fits	Check before sending
Windows	FileGizmo or free Adobe Acrobat Reader	Both support a visible signature without buying Acrobat Pro	Confirm the downloaded filename and signature page
Mac	Preview	It is built in and Apple documents typed, drawn, camera, and nearby-device signature capture	Save a copy so the original remains untouched
iPhone	Preview	Apple’s current iPhone guide includes form filling and signature controls	Zoom in after saving because a phone screen can hide placement errors
Android	FileGizmo or free Acrobat Reader mobile	Both provide a guided signature workflow; FileGizmo keeps processing in the browser	Do not mistake a simple pen annotation for a certified signature

This is not a claim that one option wins every job. Acrobat Reader is familiar and its current desktop and mobile help pages document signature workflows. Apple Preview is convenient on supported Apple devices. FileGizmo is useful when you want one interface across platforms and do not want to send the file to a processing server.

Sign a PDF on Windows

For the private browser route, open Sign PDF, choose the unlocked document, and select Type, Draw, or Upload image. Add the signature, move it on the page, and create the signed copy. No account is required, and the file stays in the browser workflow.

Adobe’s Reader documentation, updated 22 June 2026 when checked, also describes opening the E-Sign menu and choosing Fill & Sign. Reader is the better fit if an organization already supports Adobe’s interface or you need features that FileGizmo does not provide. Check Adobe’s live product terms before assuming that an advanced identity or cloud workflow is free.

Whichever route you choose, save the result as a new file. Open it in a separate reader and make sure the mark is on the intended page rather than a similarly numbered printed page.

Sign a PDF on a Mac

Open the document in Preview, show the Markup toolbar, and use the Sign control. Apple’s current Preview guide documents creating a signature with the trackpad, the Mac camera, or a nearby iPhone or iPad. Place the signature on the correct page, resize it without covering nearby text, then save a copy.

Preview is a strong first choice because it is built into macOS. FileGizmo remains useful if you prefer not to save a reusable signature in an application, need the same steps on another device, or want to upload a tightly cropped transparent PNG. Neither visible-mark route automatically creates a certificate-backed signature.

Sign a PDF on an iPhone

Apple’s current iPhone guide documents opening a PDF in Preview, selecting the form-filling control, and adding a signature. The labels can differ across iOS releases, so use Apple’s current instructions for the version installed on the phone.

After placing the mark, pinch to zoom and inspect its edges. A signature can look correctly positioned at fit-to-screen size while covering a date, checkbox, or printed name at full resolution. Save or share the completed copy only after checking every required page.

You can also use FileGizmo in a current mobile browser. Draw mode works with touch, while Type mode avoids a rough finger-drawn mark. For a long or complex form, a larger screen makes page selection and placement easier.

Sign a PDF on Android

Adobe’s mobile help, updated 9 June 2026 when checked, documents opening a PDF, choosing Fill & Sign, selecting the signature control, and placing the mark. Adobe also states that the free Acrobat Reader mobile app can be used to fill and sign forms, while paid plans cover additional features.

Google Drive can annotate PDFs on Android with a pen or highlighter and save the original or a copy. That is useful for a quick handwritten mark, but it is not the same as a reusable signature workflow, identity verification, or a certificate-backed digital signature. Use it only if the recipient accepts a visible freehand mark.

FileGizmo offers the same Type, Draw, and Upload image choices as its desktop route. Large PDFs may feel slower on a phone because local memory and processor limits are lower. Close unused tabs if the preview struggles, and keep the source file until the recipient confirms acceptance.

Use one private workflow across all four platforms

1. Keep an untouched copy of the source PDF.
2. Open Sign PDF in a current browser and choose the file from the device.
3. Type a name, draw a mark, or select a cropped PNG or JPG that you are authorized to use.
4. Place the signature on the correct PDF page. Drag it away from dates, amounts, checkboxes, and required text.
5. Create and download the signed copy.
6. Open that copy outside the tool and inspect every page at normal size and while zoomed in.

The browser reads the PDF and builds the new copy locally. You can verify the boundary in the browser Network panel: no file upload request should appear while the signature is processed. Temporary previews use local browser URLs rather than a remote document link.

If the PDF also contains fields, complete them with Fill PDF Form before signing. Some certificate signatures become invalid when a document is changed, so preserve any signed original and follow the sender’s order of operations.

Verify the signed file before sending

Check the signature page, spelling, date, initials, page count, orientation, and filename. Confirm that the mark is not clipped and that no content disappeared. If the sender provided a portal, review its preview before final submission.

Do not email a reusable signature image beside the finished document. Store that asset securely on your own device, and never place another person’s signature without authority. For identity-sensitive or high-value documents, use the recipient’s required service and obtain appropriate advice rather than relying on appearance alone.