Files are processed in your browser, not uploaded. Privacy →
Deckle
Open a PDF
Skip to guide

Privacy

How to check a PDF for hidden information before sharing

By DeckleUpdated

To check a PDF for hidden information, look in eight places: document properties, the XMP record, attachments, comments, form fields, hidden layers, text hidden under images or shapes, and the file name. Start with Remove PDF metadata, which lists the properties, XMP packet, document identifier and attachments with their values, and removes the ones you tick when you choose Remove metadata. The rest you check in your PDF reader.

Remove PDF metadata

Visible pages are one part of the review

Visible content

Words, images and repeated information

Supported metadata

Properties, XMP, identifier and attachments

Other PDF structures

Require checks beyond this metadata tool

No supported metadata found ≠ no hidden information

Conceptual scope map · the inspector's supported findings do not establish complete sanitisation of the document.

How to check a PDF for hidden information

  1. Open Remove PDF metadata and choose the PDF, or drop it onto the page. Read every value under Document properties, XMP metadata, Document identifier and Embedded attachments.
  2. Open the PDF in your reader and look at the comments panel for notes, highlights and reviewer names.
  3. Click into any form fields and check what has been typed.
  4. Open the layers panel, if your reader has one, and switch on any hidden layers.
  5. Select all the text on each page (Ctrl+A or Command-A) to reveal white or covered text, or save all the text with PDF to text and read it.
  6. Check the bookmarks and links for internal names or addresses.
  7. Look at the file name.
  8. Remove what should not go, then check the final file once more.

Where hidden information sits

Place What it can reveal How to find it How to remove it
Document properties Author, title, app names, dates Remove PDF metadata, or your reader's document properties Tick and choose Remove metadata
XMP packet A second copy of the properties, plus edit history Listed as XMP packet in Deckle Tick it
Document identifier A link between this copy and others Listed in Deckle Tick it
Attachments Whole files, such as spreadsheets or drafts Listed under Embedded attachments in Deckle Tick it, after saving any you need
Comments Reviewer names and remarks The reader's comments panel Delete them in an editor
Form fields Typed answers, sometimes in fields that print small Click into fields Clear or flatten them in an editor
Hidden layers Old versions, internal notes, alternative text The layers panel Remove the layers in the source app
Covered or white text Text under a box, behind an image or in white Select all, or extract the text Delete it in the source, or redact it
Bookmarks and links Internal file paths, intranet addresses The bookmarks panel; hover over links Fix them in the source document
File name "v7-draft-for-legal-JS.pdf" Your file manager Rename the file

Example

A 14-page proposal is ready to send to a client. Deckle lists Author j.smith, Title Proposal v7 INTERNAL, Creator Microsoft Word, an XMP packet and one embedded file, pricing-model.xlsx. The comments panel shows six notes from the sales team, and selecting all text on page 9 reveals a paragraph of internal pricing coloured white.

The fix: delete the comments and the white paragraph in the source document, export again, then run Remove PDF metadata and tick everything except a corrected title. Rename the file proposal-acme-2026.pdf.

Covering is not removing

A black or white rectangle drawn over text hides it on screen but leaves it in the file. Anyone can select it, copy it or find it with search. The same applies to text hidden under an image. To take information off a page for good, delete it in the source document and export again, or use a redaction tool that removes the content under the mark. Check by searching for a word that should be gone.

Order of work

  1. Edit the content and remove pages you do not want to share, for example with Organize PDF pages.
  2. Delete comments, clear form fields and remove hidden layers.
  3. Remove metadata with Deckle.
  4. Add a password, if needed, with Password protect PDF.
  5. Open the final file and repeat the checks above.

Each app that saves the file can add new properties, which is why metadata removal comes near the end.

Tips

  • Look at the file size. A PDF much larger than its pages suggest often has attachments or hidden images.
  • Search for your own name and your organisation's name in the final file.
  • Check every page, not just the first. Appendices and back pages collect forgotten notes.
  • Keep the full original private. Deckle never changes it, so the version with its history stays on your device.

Frequently asked questions

Does Remove PDF metadata find comments and form data?

No. It lists document properties, the XMP packet, the document identifier and attachments. Comments, form values and layers are checked in your reader.

Can a PDF contain another file?

Yes. PDFs can embed whole files as attachments. Deckle lists them under Embedded attachments with their names.

How do I find white or hidden text in a PDF?

Select all the text on the page, or save the text with PDF to text and read it. Text hidden by colour or covered by an image shows up in both.

Is the PDF uploaded when Deckle checks it?

No. The scan and the cleaned copy are made in your browser, and the file is not uploaded.

Related tools

Sources