Stamp a PDF with nothing to set up
The options card shows only Output format, fixed on PDF. You do not create an account with a timestamp authority, and there is no address to paste.
No file open
Timestamp a PDF
or drop a file anywhere here
Dropbox
Google Drive
Files other than PDF are converted first. Signing in raises the size limit.
Or start from a blank IRS form
Browse all IRS forms →- You add
- One PDF
- You set
- Nothing, indox picks the timestamp authority
- You get
- A PDF with an embedded RFC 3161 timestamp
A timestamp is a signed record, issued by a timestamp authority, that ties a document to a moment in time. Timestamp PDF requests one for your file under RFC 3161 and embeds it in a copy of the PDF, where a PDF reader can show it next to any signatures. The page has no settings. You add one PDF, select Run Timestamp PDF and download the result. indox chooses the timestamp authority on its servers, so you cannot enter an authority address of your own. One file runs without an account. The timestamp records the time at which the authority issued it, and how much weight a reader gives it depends on whether the reader trusts that authority.
What can you do when you timestamp a PDF?
Request the timestamp under RFC 3161
RFC 3161 is the protocol this tool uses to ask an authority for a timestamp. indox makes the request for you and places the authority's reply in the file.
Keep the timestamp inside the file
The timestamp is embedded in the PDF as a signature field. It travels with the copy you download, so no separate token file has to be stored beside it.
Hear about it when no authority answers
If the timestamp authority cannot be reached or refuses the request, the job ends with Couldn’t process file and the reason. You are not given an unstamped PDF labeled as finished.
What timestamping keeps and what it changes
Stays the same
- Every page and its content, exactly as uploaded.
- What the pages look like. The timestamp is not printed on them.
- The file on your device, which carries no timestamp.
Changes
- A document timestamp is added as a signature field of the RFC 3161 kind, and PDF readers list it in their signature panel.
- Only a SHA-256 hash of the document goes to the timestamp authority. The authority returns a signed time that is embedded in the copy.
- The time comes from the authority, not from your device or from anything you type.
- The authority is chosen from a list the engine allows, and the page does not let you pick one.
- Changing the stamped file afterward, for example by protecting it, breaks the timestamp.
How to timestamp a PDF in 3 steps
Add your PDF
Drop the file where the page says Drop a file here, or select Choose file. A card with the file name and a Replace button shows which PDF will be stamped.
Run the timestamp
No field needs a value. Select Run Timestamp PDF, and indox sends the request to its timestamp authority.
Save the stamped copy
When the page reports Conversion complete, select Download. Open the copy in a PDF reader to read the time and the name of the authority.
Why timestamp a PDF with indox?
Timestamp PDF keeps the task to one upload and one button. You do not register with a timestamp authority, install signing software or handle a token file, because indox makes the RFC 3161 request and embeds the answer for you. The authority address is set on the indox servers and cannot be replaced from the page, so every request goes to the place indox has chosen. A single file runs without an account. Your PDF travels to indox over HTTPS, and on the free tier the upload and the stamped copy are deleted automatically within 24 hours after the job finishes, so save your download when it is ready. If the request fails, the page says so instead of returning the file unchanged.
- No settings and no authority account to create
- RFC 3161 timestamp embedded in the PDF itself
- Timestamp authority chosen by indox
- No account needed for a single file
- A failed request ends in an error message
What are the limits when you timestamp a PDF?
- Size
- The free tier has a file size limit. Signing in raises it, and paid plans raise it further.
- Formats
- This tool works on PDF files. To change a file's type, use the PDF converter.
- Privacy
- Files are encrypted in transit and processed on indox infrastructure.
- Deletion
- Free-tier files are deleted automatically within 24 hours after the job finishes. Signed-in output stays in your history for your plan's retention period.
Limits worth knowing
- You cannot choose the timestamp authority. indox uses the one configured on its servers, or the default of its PDF engine when none is configured, and the page does not name the authority before you run the job.
- The result screen shows neither the time nor the authority. Open the stamped copy in a PDF reader to see both.
- Whether a PDF reader displays the timestamp as trusted depends on the authority's certificate and on the reader's own trust settings. This page controls neither.
- A PDF that needs a password to open cannot be stamped here, because a timestamp is a signature and a signature cannot be applied to an encrypted file. Unlock it first.
- Make the timestamp your last step. Running Protect PDF, Change Permissions or another tool that rewrites the stamped copy breaks the timestamp.
When the result is not what you expected
| What you see | Why | What to do |
|---|---|---|
| The job ends with an error | The timestamp authority could not be reached or refused the request | Try again later. No unstamped PDF is returned as finished. |
| No timestamp is visible on the page | The timestamp is stored in a signature field, not printed on the pages | Open the signature panel of a PDF reader to see it. |
| The reader says the timestamp is not trusted | Trust depends on the authority's certificate and on the reader's own settings | Check the reader's trusted certificates. This page controls neither. |
| The timestamp is gone or invalid after a later edit | Rewriting the stamped file breaks the signature | Make timestamping your last step. If you must edit, edit the original and stamp again. |
| The file asks for a password | A signature cannot be applied to an encrypted file here | Remove it with Unlock PDF, then stamp the open copy. |
What do the free and paid plans add?
Free
- All converters
- Daily credit refresh
- Email support
Basic
- Access to all features
- AI Extract
- Priority conversions
- Email support
Highest priority
Premium
- Everything in Basic
- Highest priority queue
- Larger file limits
- Priority support
Pay-As-You-Go
- No subscription
- Credits never expire
- Opt-in auto-refill
- Access to all features
What else can you do with a PDF?
Who timestamps PDFs?
Writers and designers with finished work
You want a dated copy of a manuscript, a design or a set of drawings before you share it. Stamp the final PDF and keep the stamped copy with your records.
Researchers and engineers logging results
Lab notes, test reports and specifications gain a time marker that does not rely on your own computer clock.
Teams closing a document version
After the last review round, stamp the agreed PDF so that everyone can refer to the same dated file.
When to timestamp a PDF, and when to pick another tool
- A finished document should carry a time marker issued by an outside authority.
- You file a report today and want its date recorded inside the file itself.
- A draft goes to several people, and you want one dated reference copy.
- You need a signer name and a reason stored in the file. Certificate Sign records those, and Timestamp PDF does not.
- You want the date printed on each page. This tool has no setting for visible text, so stamp a line of text with Watermark PDF instead.
Where can I read more?
Sources
- RFC 3161: Internet X.509 PKI Time-Stamp Protocol (TSP)IETF
- TimestampController source, v2.14.2Stirling-PDF on GitHub
Facts checked on October 16, 2026
Do it all with indox
No tool matches that search.
Timestamp PDF FAQs
What is an RFC 3161 timestamp?
It is a signed reply from a timestamp authority that links a file to the time of the request. RFC 3161 is the standard that defines how the request and the reply work.
Which timestamp authority does indox use?
The authority is set in the indox server configuration, and the page does not display its name. When none is set, the PDF engine falls back to its own default authority.
Can I use my own timestamp authority?
No. The page has no field for an authority address, and indox drops an address sent to it in any other way.
Where can I see the timestamp?
Open the downloaded copy in a PDF reader that has a signature panel. The timestamp is listed there as a signature field with the time and the authority that issued it.
Is the timestamp printed on the pages?
Timestamp PDF has no setting for a visible mark. It adds the timestamp as a signature field in the file, and for a date that prints you can add text with Watermark PDF.
Can I timestamp a password-protected PDF?
Not directly. Remove the password with Unlock PDF and stamp the unlocked copy, and remember that protecting that copy afterward would break the timestamp.
Do I need an account to timestamp a PDF?
No account is needed for one file, since Timestamp PDF has the free badge. Higher limits come with signing in or a paid plan.
What happens to my PDF once it has been timestamped?
Your file is sent over HTTPS. On the free tier, indox deletes the uploaded PDF and the stamped copy automatically within 24 hours after the job finishes.