How to Sign a PDF Online: Complete Guide
Signing a PDF without printing and scanning saves time and works from any device. Our free PDF signature tool lets you draw your signature using a mouse or touchscreen and embeds it as a transparent PNG image directly into the PDF using pdf-lib — entirely in your browser.
Image Signature vs. Cryptographic Digital Signature
It is important to understand the difference between these two types of signatures:
- Image-based signature (what this tool creates): A transparent PNG of your drawn signature is placed on a page of the PDF. It is visually identical to a handwritten signature on paper. It does not contain cryptographic verification, cannot detect tampering after signing, and has no audit trail.
- Cryptographic digital signature: Embeds a certificate-backed signature using public key infrastructure. Detects document tampering, creates a verifiable audit trail, and is required for regulatory compliance in many industries.
Image-based signatures are appropriate for many everyday documents — contracts between parties who both agree to sign digitally, approval forms, acknowledgment documents, and internal sign-offs. For legally regulated transactions, use a certified service like DocuSign or Adobe Sign.
How Encrypted PDFs Are Handled
If your PDF is password-protected, you will be prompted to enter the password. The file and password are securely sent to our server over HTTPS, where the encryption is removed in memory. The unlocked file is streamed back to your browser for signature embedding — we never write your file to disk, log its contents, or retain it after the operation.
Tips for a Clean Signature
- Use a stylus on a tablet for the most natural signature appearance.
- Sign slowly and deliberately on the canvas for clean results.
- Use the Clear button to retry until you are happy with how the signature looks.
- The signature is transparent — it blends naturally with any page background, including colored or textured pages.