Most PDFs carry two dates inside them: when the file was created and when it was last modified. You can see both for free in a few seconds, without uploading the file anywhere. This guide shows where to find them, why they often differ from the date your computer shows, and how to read the gap between them.
The quickest way
Attach the PDF to the free checker on our home page. It reads the file in your browser, so nothing is sent to us, and shows two big dates: Created and Modified. If the file was modified a minute or more after it was created, the Modified date turns amber and tells you how much later, for example “7 days later”.
Underneath, it lists how many times the file was saved, the author name, the app the document was made in and the software that last wrote the PDF. Times are shown in your own time zone.
Other ways to see the dates
Any good PDF viewer can show the same two dates. Look for “Document properties”.
| Where you open it | How to find the dates |
|---|---|
| Adobe Acrobat Reader | File, then Properties (Ctrl+D on Windows, Cmd+D on a Mac). The Description tab lists Created and Modified. |
| Google Chrome | Open the PDF in a tab, open the viewer’s menu (the three dots at the top right of the page) and choose Document properties. |
| Mozilla Firefox | Open the PDF, open the viewer’s menu (the » button at the top right) and choose Document Properties. |
| Preview on a Mac | Tools, then Show Inspector, then the first (information) tab. |
Viewers differ in how much they show. Most don’t tell you how many times the file was saved, or whether its second copy of the details (called XMP) agrees with the first. The checker shows both.
File dates are not PDF dates
This catches a lot of people out. Windows File Explorer and the Mac Finder show dates too, but those belong to the copy on your computer: when it was downloaded, saved or copied there. Email it to someone and their copy gets a new date. Those dates say nothing about when the document was made.
The dates inside the PDF travel with the file. Download it, email it or copy it to a memory stick, and they stay the same. That’s why they’re the ones worth reading.
How to read the two dates
- The same, or under a minute apart: the file hasn’t been saved since it was made. Many apps write both dates a few seconds apart when they first save a file.
- Modified later than created: someone opened the file and saved it again. Filling in a form, adding a comment or compressing it all count. The bigger the gap, the more it’s worth knowing why.
- Modified earlier than created: this shouldn’t happen. A wrong clock on the computer that saved it is the usual reason, but it’s worth a question.
- No dates at all: some apps don’t write them, and privacy tools remove them. A document that would normally carry its issuer’s details but has none is worth asking about.
For the everyday reasons dates look odd, from time zones to printing to PDF, see why a PDF’s dates can look wrong.
Other places a PDF keeps dates
A second copy of the details. Many PDFs store their dates twice: in the main document details and in an XMP block. An editor can update one and miss the other. The checker shows a “Second copy” line when the two disagree, which some other checkers miss because they only read one.
Earlier saves inside the file. Many editors add their changes to the end of a PDF instead of rewriting it, so the file keeps a record of how many times it was saved. More than one save means it was changed after it was first made.
The date on the page. A letter can say “1 March” on the page while the file says it was created in June. That can be innocent, such as an old letter saved as a PDF later, but it’s the kind of mismatch worth noticing.
When the dates really matter
For contracts, payslips, invoices, evidence and anything you’re relying on, the dates are a clue, not proof. Anyone with the right app can change them, and the computer that saved the file may have had the wrong time. Use them to decide what to ask, then confirm the important things with whoever issued the document.
If you’d like a person to look at a file for signs of editing or backdating, Document Check is our paid check, done by hand, with the result emailed to you. It reports signs, never proof, and says so plainly.
Frequently asked questions
Can you see when a PDF was created?
Usually, yes. Most PDFs record a created date. Attach the file to the free checker, or open Document properties in your PDF viewer.
Does opening a PDF change its modified date?
No. Opening and reading a PDF doesn’t change it. Saving it does, and some viewers save when you fill in a form or add a comment.
Why does my computer show a different date?
Your computer shows when that copy of the file was saved to it, for example when you downloaded it. The PDF’s own created and modified dates are inside the file and don’t change when it’s copied.
Can a PDF’s created date be changed?
Yes. Editing software can change it, so a date that looks right isn’t proof. That’s why the important checks are with the person or organisation that issued the document. PDF Check’s own tools never change a file’s dates.
