OmniDocHow to Digitally Sign a PDF and How It Differs
Learn how to digital sign a PDF in OmniDoc, how visual e-signatures differ from certificate-based digital signatures, and which one your recipient needs.
If someone sends you a PDF contract, approval form or agreement to sign, you will quickly run into two terms: electronic signature and digital signature. People use them interchangeably, and that causes trouble when the other party asks for a specific kind. This guide explains the difference and shows how to digital sign a PDF in OmniDoc without guessing which type you need.
A visual signature is a mark placed on the page, such as an image of your handwritten name. A digital signature is cryptographic: it is tied to a digital ID issued by a certificate authority, and it can show whether the file was changed after signing. Which one you need depends on who will rely on the document and what their process requires.
By the end, you will know which kind fits your situation, what to check before you sign, how to add a signature or send a sign request in OmniDoc, and how to confirm the signed copy is correct.
Which signature do you need to digital sign a PDF? The short answer
For most internal sign-offs, a visual signature added in OmniDoc is enough. If the recipient requires a certificate-based digital signature, you need a digital ID from a certificate authority and software that can apply it, because OmniDoc's sign feature, as described here, does not create or issue digital IDs.
| Your situation | What to do | Why |
|---|---|---|
| You sign your own copy of a form, approval or agreement | Add your signature in the PDF editor and save a new copy | Fits common internal sign-offs and needs no outside setup |
| Several people must sign the same PDF | Send a sign request so each person signs online | Each signer completes their part without you editing the file for them |
| The recipient requires a certificate-based digital signature | Obtain a digital ID from a certificate authority and sign with software that supports it | Only a cryptographic signature ties the mark to a verified identity |
| You must show the document was not changed after signing | Use a certificate-based signature and ask the recipient to verify it in their PDF reader | A visual mark alone does not reveal later edits |
| You are not sure what the other party expects | Ask which type they accept before you sign | Avoids re-signing and delays later in the process |
Before you digital sign a PDF
Check these points first. Each one prevents a common problem.
- Confirm the required signature type. A visual signature will not satisfy a requirement for a certificate-based digital signature. Ask the sender directly, and get the answer in writing if the document has legal or contract weight.
- Finalize the text. Make any edits before signing. A change after signing can invalidate a certificate-based signature, and it can make a visual signature misleading because the signed page no longer matches what you agreed to.
- Start the digital ID process early if you need one. A certificate authority issues digital IDs after checking your identity, so the timing depends on the issuer. Do not wait until the deadline to request one.
- Prepare your signature. Have the signature image or mark ready so you can place it on the page without rushing.
- Check whether the PDF is scanned. A scanned PDF is an image of each page, so you can still place a signature on it. If you need to select or edit its text first, run OCR in the PDF editor. To check, try selecting a line of text: if nothing highlights, the page is probably an image.
Adding a signature to a PDF in OmniDoc, step by step
These steps cover adding your own signature and sending a sign request. They assume you have the OmniDoc desktop client, which you can get at download.omnidoc.top.
- Open the PDF in the OmniDoc desktop client. The sign feature is part of the PDF editor, so open the file there rather than in another viewer.
- Choose the sign option in the PDF editor. This lets you create or select the signature you want to place on the page.
- Place the signature on the signature line. Click where the signature belongs. Placing it on the correct line matters more than the exact size, because a misplaced mark can be mistaken for an approval of different text.
- Adjust the size and position. Keep the signature inside the signature block and avoid covering printed text.
- Save the signed file as a new copy. Keep the original unsigned so you can compare the two later.
- To get several signatures, send a sign request. Upload the PDF to the sign request feature, add each recipient, and send it. Each person signs online, so you do not need to collect the file back and forth by email.
- Confirm the request went to the right people. Review the recipient list before sending. If you spot a wrong address after sending, send a new request to the correct address rather than assuming the first one will be corrected.
If the recipient needs a certificate-based digital signature, the steps above do not create one. Obtain your digital ID from a certificate authority first, then use software that applies it to the PDF. Confirm that tool with the recipient before you start.
Check the result
Before you send the signed PDF, check the following.
| Check | How to see it | If it's wrong |
|---|---|---|
| The signature is on the correct line | Open the saved copy and scroll to the signature block | Remove the mark, place it again, and save a new copy |
| No other content changed | Use the compare two PDFs feature in the PDF editor to check the signed copy against the original | Return to the original, make any needed edits, and sign again |
| You signed the final version | Check the file name, version or date against the version the sender approved | Sign the correct version and tell the sender which copy you signed |
| A certificate-based signature is valid | Open the file in a PDF reader that shows signature status and check the signer and whether the file changed | If the reader shows the file changed or the status is unknown, ask the signer to sign again with a valid digital ID |
| Sign requests reached the right people | Compare the recipient list with the names you expected | Send a new request to the correct address |
🎯 Which approach fits you?
- You need a signature on a document you control. Add a visual signature in the PDF editor and save a copy. This suits internal approvals and forms where the recipient only needs to see your mark.
- Several people must sign. Use a sign request so each person completes their own signature online.
- The recipient requires proof of identity or a tamper check. Get a digital ID from a certificate authority and use a signing tool that supports it. OmniDoc's sign feature covers visual signatures and sign requests, so do not rely on it for this requirement without confirming with the recipient.
❓ FAQ
1. Can I digital sign a PDF for free?
OmniDoc's pricing is not covered here, so check the terms on the site before you rely on any tool. When you compare free options in general, look at file size limits, whether a watermark is added, whether your file is uploaded to a server, and whether the layout survives signing. For a certificate-based digital signature, also confirm whether the tool accepts your digital ID, because a free visual tool may not provide that.
2. Can I sign a scanned PDF?
Yes. A scanned PDF is an image of each page, so you can place a signature on it. If you need to select or change its text before signing, run OCR in the PDF editor first.
3. Does a visual signature prove who signed?
No. A visual signature shows that a mark was placed on the page, but it does not verify the signer's identity or show whether the file changed later. If the recipient needs that assurance, ask for a certificate-based digital signature.
4. Where do I get a digital ID?
A certificate authority issues digital IDs after verifying your identity. Ask the recipient which issuers they accept, because requirements differ between organizations and countries.
📝 Summary
Visual e-signatures and certificate-based digital signatures serve different purposes, so confirm which one the recipient needs before you digital sign a PDF. In OmniDoc, you can add your signature in the PDF editor, send sign requests for others to complete online, and then check the saved copy against the original.
