How to Sign a PDF Online Free (and When You Need a DSC Instead)

Sign a PDF without printing or scanning

The old way of signing a PDF was to print it, sign with a pen, scan it and email the scan back. That wastes paper and time, and the scan is often crooked and heavy. Sign PDF lets you place a signature directly on the document in your browser, and the file never leaves your device.

You can create your signature in three ways:

TipFor the cleanest image signature, sign in dark blue or black ink on plain white paper, photograph it in good daylight without shadows, and crop tightly around the signature before uploading.

Electronic signature vs digital signature (DSC)

People often use 'e-signature' and 'digital signature' as if they meant the same thing. They do not, and the difference matters.

• A visual electronic signature is an image or mark of your signature placed on the page. That is what Sign PDF creates. It shows intent to sign, just like a scanned pen signature, but it does not mathematically prove who signed or that the document has not been changed since.
• A certificate-based digital signature (DSC) uses a digital certificate issued to you by a licensed Certifying Authority, usually stored on a USB token. Signing with it embeds cryptographic data in the PDF. A PDF reader can then check who signed and whether the file has been altered afterwards.
• Aadhaar eSign is an online service in India where you authenticate with your Aadhaar (typically using an OTP) through an authorised eSign service provider, and a short-lived certificate is used to sign the document. It is also certificate-based and verifiable.

Watch outA signature added with Sign PDF is a visual signature only. It is not a DSC and not Aadhaar eSign, and it should not be used where a law, regulator or organisation requires a certificate-based digital signature.

When a visual signature is usually fine

For a large share of everyday paperwork, the other side simply needs to see that you have read and agreed to the document. A visual signature is commonly accepted for:

• Accepting an offer letter or appointment letter.
• Signing a non-disclosure agreement with a client or freelancer.
• Internal approvals, purchase orders and expense claims.
• Consent forms and declarations for schools, colleges and events.
• Rental agreements and quotations between individuals or small businesses, where both sides agree to sign this way.

Even in these cases, the deciding factor is what the person or organisation receiving the document will accept. If they ask for a 'wet' signature, a DSC or eSign, a visual signature will not do.

When Indian processes typically need a DSC or Aadhaar eSign

India's Information Technology Act recognises electronic signatures that meet its requirements, such as DSCs and Aadhaar eSign. Many official processes ask specifically for these. Common examples include:

• Company and LLP filings with the Ministry of Corporate Affairs, which generally require a DSC from directors or designated partners.
• GST returns for companies and LLPs, which typically require a DSC. Other taxpayers may be allowed to use an Aadhaar-based or EVC option instead.
• Income tax filings where a DSC is mandated, such as some audited cases. Many individuals can instead verify their return electronically through Aadhaar OTP or net banking.
• Government e-tenders and e-procurement portals, which usually require a class of DSC specified by the portal.
• Some bank, insurance and lending journeys that use Aadhaar eSign to sign loan or account documents online.

Rules change and differ between departments, so treat this list as examples, not a complete or current legal reference. Always check the latest instructions from the portal, department or organisation you are submitting to, or ask your chartered accountant or company secretary.

Watch outCertain documents may not be valid when signed electronically at all, and may still need a physical signature, stamp paper or registration. Wills and property sale documents are common examples. If you are unsure, ask a lawyer before relying on any electronic signature.

Make your signed PDF harder to misuse

A visual signature is easy to copy from one document to another. That is true of a scanned pen signature too, but it is worth taking a few precautions:

1. Sign only the final version. Make all edits first with Edit PDF, then sign last.
2. Add the date and context. Writing the date and a short note next to your signature, such as 'Accepted on 13 Oct 2026', makes reuse harder.
3. Sign every page if the document asks for it. Some agreements require initials on each page to show no page was swapped.
4. Protect the file. For confidential agreements, add a password with Encrypt PDF before emailing and share the password separately. Our guide to password-protecting a PDF shows how.
5. Do not leave a signature image lying around. Store your signature file somewhere private, not on a shared desktop or in a public folder.

Because Sign PDF runs inside your browser, your signature and your document are never uploaded to a server. That is one less place your signature image can end up.

Troubleshooting common signing problems

• The signature looks pixelated. Upload a larger, sharper image, or draw it at a bigger size and then shrink it on the page.
• There is a grey or white box around the signature. The photo had a coloured background. Retake it on bright white paper in good light, or crop more tightly.
• The PDF will not open because it is password-protected. Open it with the password first. If it is your own file, use Remove PDF password, sign it, then re-protect it if needed.
• The recipient asks for a 'digitally signed' PDF. Ask whether they mean a DSC or Aadhaar eSign. If so, a visual signature will not meet their requirement.
• The file is too large to send afterwards. Run it through Compress PDF. Our guide on PDFs too large for email covers more options.