Sign a PDF in your browser instead of on someone else's server

Signing a contract usually means handing a contract to a signing service. That is a strange default. The document you are least willing to lose control of is the one you are asked to upload, to a company whose only involvement in the relationship is drawing a squiggle on page nine.

Two different things are called "signing"

The vocabulary causes most of the confusion here.

An electronic signature is a mark indicating intent: a drawn squiggle, a typed name in a script font, an uploaded image of a wet signature. Its legal weight, in most jurisdictions that recognise electronic signatures, comes from the surrounding evidence — the email thread, the agreed terms, the audit record, the conduct of both parties — rather than from anything technical inside the PDF. For the overwhelming majority of documents people sign, this is what is wanted and what is accepted.

A digital signature is a cryptographic operation. A hash of the document is signed with a private key belonging to a certificate that a trust store recognises, and the result is embedded in the file. A reader can then verify two distinct things: that the document has not changed since signing, and that the signature was produced by the holder of that certificate. This requires a certificate you have obtained and can protect, and it is the right answer for regulated filings and high-value agreements — not for a school permission slip.

The PDF signing tool covers the first case: draw with a trackpad or touchscreen, type a name, or place an image of your signature, and position it precisely on the page. In this browser workflow, the selected document is not uploaded for signing, so the operation does not create a product-server copy of the contract.

Do the form fields first

Order matters more than people expect. If the document has interactive fields — dates, names, initials, checkboxes — complete them with the form filling tool before placing your signature.

Two reasons. First, signature annotations are positioned in page coordinates, and some readers reflow or repaint field content in ways that can visually collide with a mark placed earlier. Second, if you later apply a cryptographic signature, every edit after that point invalidates it; establishing the habit of "fill, then sign, then stop" avoids an entire category of confusion.

If the document has no interactive fields at all — a flat scan with printed lines to write on — you are dealing with a different problem, and typed text has to be placed as new content rather than typed into a field.

Place the mark properly

Small details separate a signature that reads as deliberate from one that reads as an accident:

• Match the baseline. Sit the mark on the printed signature line, not floating above it or crashing through the name underneath.
• Size it to the space. A signature two-thirds the width of the provided line looks right; one that spills into the adjacent date field does not.
• Use a transparent background. An uploaded photograph of a signature on white paper produces a white rectangle over the page. Remove the background or draw the signature directly.
• Draw at a comfortable size and let it scale down. Signing large and reducing produces smoother curves than trying to sign inside a small box.
• Fill in the date yourself. Do not assume the recipient's software will stamp one.

Flatten before you send

An unflattened signature is an annotation object layered over the page. In practice that means a recipient can select it, move it, or delete it in a capable editor, and some readers will not print annotations at all by default.

Running the finished file through the flattening tool merges annotations and filled field values into the page content itself. After flattening, the signature is simply part of the page: it prints everywhere, displays identically in every reader, and cannot be dragged off.

Keep an unflattened copy if you might need to correct a field. Flattening is a one-way operation by design.

Sensible habits around signed documents

• Verify before signing, not after. Read the version you are about to sign, not the draft that was circulated last week. If in doubt, compare them.
• Never sign a document you cannot fully read. A scanned page with a low-resolution clause is not something to put your name on.
• Keep the signed original. The copy you send is not your record; the file you exported is.
• Encrypt it for delivery if the contents are confidential. Signing does not make a document private, and an executed agreement is usually more sensitive than the draft was.
• Check the metadata. A signed contract carrying the author name and file path from your internal template folder tells the counterparty more than you intended.

None of this requires a subscription, an account, or an upload. It requires doing the steps in the right order and keeping the file in your own hands while you do them.