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A password-protected PDF cannot be faxed as-is: online fax services must render your document into a plain image before sending, and encryption blocks that step. Remove the password first (only possible if you know it), then fax the decrypted file. Note: a fax is never encrypted in transit, so strip the password only when you are ready to send.
You have three ways to get the password off:
A fax machine never receives a PDF. Online fax services convert your document into a black-and-white image (technically a TIFF bitmap) and transmit that picture over the phone line. Rendering an image requires reading the file's contents, and a password-protected PDF refuses to be read until the password is supplied. The conversion software does not have a way to type in your password, so the step fails. Here is the part that confuses people: most services do not tell you the file was encrypted. They report a generic "conversion error" or "document failed to process", and users assume the file is corrupted. If your fax keeps failing on a file that opens fine on your screen, a password is the most likely cause.
PDFs carry two kinds of password, and they behave differently:
| Type | What it does | How to tell |
|---|---|---|
| Open (user) password | The file will not open at all without it | Your viewer asks for a password before showing anything |
| Permissions (owner) password | The file opens, but printing, copying, or editing is blocked | The viewer shows the pages but refuses to print or shows a lock icon |
This distinction matters because it creates a trap. You might open the PDF, see every page, and assume it will fax. But if a permissions password blocks printing, the print-to-PDF trick fails too: the viewer will not produce the new file. The removal methods above need the right password. The open password comes from whoever sent you the file. The permissions password is often the same one, but if the sender set a different owner password, only they can hand it to you. There is no legitimate way around either one if you do not have the password.
Understand what you are doing: a fax is sent as an unencrypted image over the telephone network. Whoever protected that PDF did so because the contents are sensitive. The protection is gone the moment the fax transmits, so the sensitive file should not sit around unprotected beforehand. Remove the password, send the fax, and delete the decrypted copy right after. The biggest real-world mistake is decrypting the file "to make it easier" and leaving the decrypted copy in a downloads folder for weeks.
One more option for especially sensitive documents: skip the fax. A mailed letter with tracking (LetterAgent sends letters to US and Canadian addresses with a certified or registered option) keeps the document as a physical original rather than an unencrypted phone transmission. If the recipient genuinely needs the file by fax, that trade-off is on them, but for documents where you control the delivery method, physical mail with proof of delivery is often the stronger choice.
LetterAgent's fax feature is currently in testing (activation is in progress), so treat it as available in testing rather than a service you can count on today. When it is active, you send a fax by asking your AI assistant: you get a per-fax quote with the page count verified, approve the exact total, pay once through Stripe, and the fax is sent. It covers US and Canadian fax numbers only, with no inbound faxes. Make sure any PDF you hand over is already decrypted before you quote it, since a protected file will fail the conversion step.
Ready to fax it? Fax with LetterAgent: describe it to your AI assistant, approve the exact quoted price, and it is sent.
LetterAgent is a working name. Prices include print, postage, and our service fee. US prices in USD, Canadian prices in CAD (Canadian prices exclude applicable sales tax, added at checkout). Currently in private testing.
Need help? Ask your assistant: it can check a job's status any time. If it ever can't handle something: hello@getletteragent.com