Electronic Signature vs Qualified Digital Signature
Not all digital signatures are equivalent in legal weight, and the distinction matters for different document types.
A simple electronic signature — which includes placing a signature image on a PDF, typing your name in a signature field, or clicking an "I agree" button — carries legal validity in most jurisdictions for private contracts, provided both parties agree to the method. This covers most everyday use cases: NDAs, freelance contracts, rental agreements, and internal HR documents. The legal principle in most countries (including eIDAS in the EU) is that a signature cannot be invalidated solely because it's in electronic form. What determines validity is whether the parties intended to be bound by the document.
A qualified digital signature (QDS) is a different instrument: a cryptographically verifiable signature backed by a certificate issued by an accredited Trust Service Provider (TSP). Under eIDAS in the EU, a QDS has the same legal effect as a handwritten signature, including for notarial acts, public procurement contracts, and court submissions. Obtaining a QDS requires identity verification with an accredited provider and typically costs €20–100 per year. For everyday business documents, the simpler methods below are sufficient and legally sound.
Methods Without Paid Software
macOS Preview is the most frictionless option for Mac users. Open the PDF, click the markup toolbar icon (the pencil-in-a-circle icon at the top right), click the signature icon, and either draw your signature on the trackpad, sign on a piece of paper and hold it to the camera, or type a stylized version of your name. Preview saves the signature for reuse. Position and resize it on the page, then save the PDF.
Adobe Acrobat Reader (free version) is the cross-platform standard. Go to Tools > Fill & Sign > Sign Yourself > Add Signature. You can draw a signature with a mouse or trackpad, type a cursive-rendered version of your name, or upload an image of your signature. The result is embedded in the PDF and the file can be saved locally without creating an Adobe account (though Adobe offers this).
Browser-based tools require no software installation: upload the PDF, place your signature using the web interface, and download the signed file. For documents you're processing frequently, this is the fastest zero-install workflow.
Adding a Handwritten Signature Image to a PDF
For users who want a genuine handwritten appearance — which can be important for personal documents and some business contexts — the cleanest method is creating a reusable signature image.
Sign your name on a blank white sheet of paper with a black or dark blue pen. Use a thicker pen stroke than you would normally — fine ballpoint signatures often photograph with too little contrast. Photograph the signature with diffuse, even lighting (no flash, near a window works well). Crop the image tightly to just the signature.
Remove the white background: in any image editor or online background remover, isolate the signature on a transparent layer and save as PNG with transparency. This produces a signature image that can be placed over any background color without an obvious white rectangle showing.
Insert the PNG on the relevant page of the PDF. Most PDF tools support placing an image at a specific position and scaling it to fit the signature line. Save the PDF — the signature is now embedded and will appear in all PDF viewers without requiring the original PNG.
Extracting the Signature Page Before Sending
In many contract workflows, the full document contains confidential schedules, pricing terms, or internal notes that the counterparty doesn't need to see. The counterparty only needs to review and sign the signature page — or at most, the main agreement text without the confidential annexes.
Extracting just the signature page before sending it for signature reduces the risk of accidentally disclosing confidential content. The workflow: extract the signature page (or the pages designated for signature) from the full contract, send the extracted PDF to the counterparty for signature, receive the signed page back, and merge it back into the full document for your own records.
This practice is standard in commercial real estate, investment agreements, and any multi-party transaction where different parties need to sign the same document but don't all need to see the complete terms. It's also useful for NDAs where you want to confirm the counterparty received and signed the document without exposing any attached confidential disclosure schedules.