LetterAgent
Mail physical letters by just asking your AI assistant.
Home > Guides > Combine PDFs into one fax
Merge your files into a single PDF before you send, with the cover sheet first and the supporting documents in the order the recipient expects. That one combined file becomes the fax, pages in order, with a page count that matches your cover sheet. Sending each document as a separate fax is the usual alternative, but it buries the recipient in separate transmissions and separate confirmation pages.
| Approach | How it works | Best when |
|---|---|---|
| Built-in PDF merge (Preview on Mac, Print to PDF on Windows) | Open the files, insert or print pages into one document | You have a computer and a few minutes; nothing to install |
| Phone scanner apps | Scan paper pages in order, export as one PDF | The documents are paper and you are working from your phone |
| Online merge tools | Upload files, reorder pages, download the combined PDF | Quick one-off jobs; avoid these for anything sensitive |
Cover sheet first, always. Then the main document the recipient is actually being asked to act on: the form, the application, the authorization. Supporting material goes after, in the order the form or the recipient's instructions list it: ID after the application, test results after the referral, invoices after the claim form. If the recipient gave you a checklist, follow it page for page; the person processing your fax is matching pages against that list, and out-of-order documents slow them down or get misfiled.
Number the supporting pages if there are more than a few. A small "page 2 of 9" in the corner costs you ten seconds and saves the recipient from guessing whether everything arrived. Update your cover sheet's page count to include every page, cover included: the confirmation page will report the total, and the two numbers should agree.
Size is the main enemy. Fax machines and online fax services handle long transmissions fine up to a point, but a 60-page fax is slow, error-prone, and more likely to fail partway through, which can mean the recipient gets pages 1 through 40 and never knows about 41 through 60. For anything over about 20 pages, consider whether the recipient actually needs all of it by fax, or whether some of it can go by mail or secure upload instead.
Quality is the second enemy. Merging does not improve your source documents: a blurry phone scan stays blurry, and faxing degrades it further. Scan at a reasonable resolution, keep pages upright and uncropped, and avoid mixing color photos into a fax full of text; they transmit slowly and print as muddy gray. If a page is illegible in your PDF, it will be worse on the other end.
Password protection is a quiet third enemy. A password-protected PDF will not convert on most online fax services: the upload looks fine, the transmission fails, and the error message rarely explains why. Remove the password from your working copy before you merge (keep the protected original for your records), or print the protected file to a fresh PDF, which drops the encryption. Either way, check that the merged file opens cleanly before you send it.
Once you have a single PDF in the right order with a matching page count, the fax itself is the easy part. If you use an online fax service, upload the PDF, enter the destination number, and send; the service converts and transmits it in one go. Through LetterAgent, describe the fax to your AI assistant, approve the exact quoted price for the verified page count, and it is sent. Either way, save the confirmation page: with a multi-document fax, that page count is the only proof that everything you assembled actually arrived.
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