How do I check my PDF files?

Last reviewed: September 27, 2026 · Markdown version

"Check my PDF" usually means one of four questions, and they are worth asking in order: is it really a PDF, does it open, does it hold real text, and is it safe to open. Each one has a quick test, and a failure at one step explains the trouble at the next. If you only want the text question answered, our free Is your PDF searchable? tool checks a file in your browser without uploading it.

1. Is it really a PDF?

Start with the name — the whole name. File Explorer may not be showing the extension at all, and Microsoft's fix for that is: "In File Explorer, select View > Show > File name extensions." Microsoft also warns that renaming does nothing to the contents: "You can change a file name extension, but that won't convert the file to another format" (Common file name extensions in Windows, read 27 September 2026). So a file called statement.pdf that is really a web page or a Word document stays one.

The file itself can settle it. The PDF standard says "The first line of a PDF file shall be a header consisting of the 5 characters %PDF– followed by a version number", and that "The last line of the file shall contain only the end-of-file marker, %%EOF" (PDF 32000-1:2008, §7.5.2 and §7.5.5, read 27 September 2026). Open the file in a plain text editor and look at the first few characters. If they are not %PDF, it is not a PDF whatever its name says. If the start is right but there is no %%EOF near the very end, our reading is that the file is incomplete — a download or a copy that stopped partway.

2. Does it open?

If one app refuses the file, try a second before you decide the file is broken. A browser is the easiest second opinion: Chrome's settings offer a choice between "Download PDFs" and "Open PDFs in Chrome", under Privacy and security, Site Settings, Additional content settings, PDF documents (Download a file — Google Chrome Help, read 27 September 2026). A file that fails everywhere is damaged or incomplete, and step 1 usually shows which. A file that asks for a password is a different case with its own rules — what a password does to a PDF.

3. Does it hold real text?

A PDF can look perfect and still be a photograph of a page, which is why a search inside it finds nothing. Drag across a line of text: if individual words highlight, there is text; if the whole page selects as one block, it is an image. The longer version of this test, and what to do when the answer is no.

4. Is it safe to open?

The US cybersecurity agency CISA's advice on attachments is old — the page is marked archived and dated 2021 — but its core points still read well: "Be wary of unsolicited attachments, even from people you know", and "Save and scan any attachments before opening them." It goes further than most: "If an email or email attachment seems suspicious, don't open it, even if your antivirus software indicates that the message is clean" (Using Caution with Email Attachments, read 27 September 2026).

Two habits from the steps above help here too. With extensions showing, a name like invoice.pdf.exe gives itself away. And a service that previews files may warn you first: Google Drive's help says "If you try to open a suspicious file, you may get a warning message. Use caution if you open the file" (View & open files — Google Drive Help, read 27 September 2026).

Checking a whole folder at once

For a phone full of PDFs, DocFind does steps 2 and 3 as a side effect of indexing them. If a file can't be opened, hasn't been read yet, or has changed since it was indexed, DocFind tells you which ones and why. Scanned pages are read on the device, matches found that way are labelled, and pages that couldn't be made searchable are reported rather than skipped in silence.

What it is not: a virus scanner — it does nothing for step 4. It reads PDFs only. A PDF that needs a password to open (a user password) is refused, while one that carries only an owner password, restricting printing or copying, is indexed like any other file.

Related: Does my PDF have a text layer? · Searching a password-protected PDF · Make a scanned PDF searchable · PDF search not finding words that are there?