← All posts

How to edit a PDF someone emailed you

A quote, a contract, a nursery form. It arrived as an attachment, one line in it is wrong or blank, and it has to go back today. You clicked it, it opened, and there is nowhere to type.

Or the toolbar is greyed out. Or there is a yellow bar across the top of the window. Or you typed into it quite happily, saved, closed it, and now cannot find the edited file anywhere on your machine.

Very little of this is about PDFs. Most of it is about where the copy you are looking at actually lives, and who marked it read-only — which is usually your own computer rather than the sender. Four checks, in order. The first one fixes about half of these on its own.

Why the copy in your inbox is read-only

Three different mechanisms produce the same symptom, which is why the advice you find contradicts itself.

The preview is a rendering, not the file. Gmail's viewer, Outlook on the web, Quick Look in macOS Mail and every phone mail app draw the attachment for reading. The bytes are still on the mail server. There is nothing on your disk to write over, so nothing offers to save.

A file opened straight from a message is a temporary copy. Double-click an attachment in Outlook on Windows and it is written into a cache folder — under %LOCALAPPDATA%\Microsoft\Windows\INetCache\Content.Outlook\, in a directory with a random name — and opened from there. You can edit that copy. You can save it. It is not the attachment, it is not in your reply, and the folder gets cleared.

A file that came from the internet is marked as such. Windows tags downloads and mail attachments with a "this came from elsewhere" flag, and Acrobat responds by opening anything so tagged in Protected View: a sandbox where the document is displayed and the editing tools are disabled. The yellow bar saying Enable Editing or Enable All Features is that, not a restriction the sender applied.

Check 1: get the file onto your own disk

Before anything else, put a real file in a real folder.

Then, on Windows, if you see a Protected View bar: click Enable Editing, or right-click the file → Properties → tick Unblock → OK. That clears the flag permanently for that file.

Check 2: is there any text in it, or is it a picture of one

Try to select a word with the mouse. If the cursor sweeps across the page and nothing highlights, there is no text layer, and no editor on earth will let you retype a line that does not exist as text.

Emailed documents skew heavily towards this. A contract that was printed, signed, scanned and sent back is a stack of photographs, as is anything from a fax-to-email gateway or a phone. It looks exactly like a typed document.

Our PDF inspector answers this in seconds, in your browser — nothing is uploaded, which matters when the document is someone else's contract and you are on a work laptop. It reads the page count, the PDF version, whether the file is encrypted, and whether there is a real text layer. For a page-by-page answer — three scanned exhibits inside two hundred typed pages — OCR PDF reports which pages are text, which are pictures and which are blank. Read its page before you upload, though: it does not add a text layer, because the Tesseract engine is not installed here, so the file comes back byte for byte as it went in with a report attached. If your file is a scan you can still sign it, annotate it and rearrange its pages, but not retype its words. The other reasons text refuses to be selected are set out separately.

Check 3: locked — and which of the two kinds

Two quite different things get called locked, and the fix differs.

Encrypted with an open password. Your reader asks for a password before showing you anything. Until it is supplied nothing can read the file — the inspector reports it as encrypted and says the text layer could not be checked, for that reason.

Permission flags. The document opens straight away and then refuses to print, copy or be changed. There is no password for you to type; the sender set flags inside the file and well-behaved readers honour them. That is a request rather than a lock — and it is the sender saying something, so decide whether you should be editing before working out how.

Either way, Unlock PDF writes the document back out with no security dictionary at all. Type the password you already use to open the file; if it opens without asking but will not let you print, leave the box empty. It is not password recovery — nothing here guesses or attacks anything, and a file whose password you do not know stays closed. Locally, the same job is qpdf --decrypt --password=thepassword in.pdf out.pdf.

Do this before you open the editor, not after. A password-protected file is refused outright with "That PDF is password-protected. Remove the password and upload it again."

Check 4: is the thing you want to change a form field

Click on it. If it highlights as a box with a cursor in it, it is a form field and you simply type. If the page has fields but they will not accept anything, the sender flattened them — the answers are page content now, and changing them is a text edit like any other.

Now edit it

  1. Open the file in our PDF editor and read the banner. It tells you if the document is signed (applying changes ends the signature), if it is an XFA form (fields cannot be edited here), or if it was encrypted (your download is saved without the encryption).
  2. Click the line you need to change and retype it. The document's own font is already selected in the font menu, marked (original).
  3. Fill in fields, place a signature, delete or add an image, rotate or reorder pages as needed.
  4. Apply, then download before you close the tab — the edit plan is kept in your browser while you work, but applying clears it, and there is no job history to go back to.

Sending it back

Two habits save an exchange of emails.

Lock the answers if it was a form. Run the finished file through Flatten PDF: the field values are drawn into the page and the fields removed, so nobody downstream can retype your figures or clear them by accident. Keep the unflattened copy — flattening is one-way.

Change the file name. If you reply with Quotation-4471.pdf and so did they, one of the two copies gets opened by mistake within the week. Rename PDF gives it a new name and, by default, sets the document title inside the file to match, which is what the recipient's reader shows in its tab. And if the file grew — an edit that re-renders a scanned page usually makes it bigger — Compress PDF before it hits their attachment limit.

If the attachment will not open at all

A forward that was truncated in transit, or a download that stopped early, gives you a file that is the right length in the folder listing and unreadable everywhere else. Repair PDF rebuilds what is reachable and tells you what was not, but it cannot invent bytes that never arrived. If the file is zero bytes, or nearly, ask for it again — preferably as a link rather than an attachment.

When the "attachment" is a photo of a document

Half of these arrive as a JPEG from someone's phone. JPG to PDF turns the photos into one PDF, a page each, and it reads the EXIF orientation flag — so a page photographed sideways comes out the right way up rather than on its side, which is not what most converters do. What you get is still a picture of a document, so check 2 applies to it from then on.

When something already on your machine is better

Nothing has to be uploaded for any of this, and for a confidential attachment that is the point:

The order is what matters more than the tool. Get a real file onto your disk, find out whether it contains text, take off whatever is locked, and only then start typing. Doing those in the other order is how an afternoon disappears into a temporary folder.

Tools this post uses: