Someone emails you a PDF and asks you to "fill this in and send it back". It sounds like one action. In practice it is four — open it in something that can type into it, fill it, make sure the answers are actually saved into the file, and attach the right version to a reply. Most of the frustration people have with this comes from step three, where a form looks filled on screen and arrives blank at the other end. Here is the whole loop, on a laptop and on a phone, without buying anything.
Open the PDF in a tool that can write to it, fill the fields, then save or download a new copy — do not just close the preview. Attach that saved copy to your reply. If the file has no typeable fields, add text on top of it and export a flattened PDF, which is what makes your answers permanent for the recipient.
Why does this work on some PDFs and not others?
Because "PDF form" means two different things.
An interactive form (an AcroForm) has real fields built into it. Click and a cursor appears. These are the easy ones — most browsers, Preview on a Mac, and any PDF app can fill them.
A flat form is a picture of a form. It was scanned, printed-to-PDF, or exported without the form layer. There is nothing to click, so filling it means placing text on top of the page at the right coordinates. Everything that goes wrong with "I can't type in this PDF" traces back to this distinction, which we unpack in why a PDF won't let you type.
Check which one you have before choosing a tool: open it and click a blank line. Cursor means interactive. Nothing means flat.
How do I fill it out on a computer?
For an interactive form, the shortest path is the one already installed:
- Save the attachment first. Filling a PDF inside the email preview pane is the single most common way to lose the work — the preview often has no save at all.
- Open it in Chrome, Edge, or Preview and fill the fields.
- Save As, or Download — a separate action from closing the tab. This is the step people skip. If your reply attaches the original file rather than the saved one, the recipient gets an empty form.
- Reply and attach the saved copy. Rename it to something that identifies you:
W-9-Jordan-Reyes.pdfbeatsform(3).pdffor whoever is filing it.
For a flat form, a browser cannot help — there is nothing to fill. You need something that places text onto the page. That is what filling any PDF online covers, and it is the case Filly is built for: upload the flat PDF, let it read the page, place the values, and export a normal PDF that anyone can open.
Why did my answers disappear after I sent it?
Almost always one of three things:
- You filled the preview, not the file. Gmail, Outlook and macOS Quick Look will happily let you type into a form and then discard it. Save the file to disk first, every time.
- You saved, but the recipient opened it somewhere that ignores the form layer. Some viewers — particularly older ones and a few mobile mail clients — render the page but not the field values.
- The fields were never committed. A field you typed into but never tabbed out of can be left uncommitted when the file closes.
The fix for all three is the same: flatten before sending. Flattening burns the values into the page so they are part of the document rather than a layer on top. The tradeoff is that a flattened form can no longer be edited — which is usually exactly what you want when returning it. We go through the failure modes in why a PDF won't save the answers you typed.
Before you hit send, do the check that costs ten seconds: close the file, reopen it from the folder, and look. What you see is what they will see.
Can I do the whole thing from my phone?
Yes, and for a single form it is often faster. On iOS, open the attachment, use Markup to type and sign, then share straight back into a reply. On Android, most mail apps hand the PDF to a viewer that can fill and re-share. Both work well for interactive forms and short flat ones. Where phones struggle is a long form or a form you fill repeatedly — thumb-typing forty fields is not a workflow. The detail is in filling and signing a PDF on your phone.
What if I send the same form back over and over?
This is where the manual loop stops being reasonable. If you return the same intake form, job application, or liability waiver for a different person every week, you are retyping the same categories of information into a new blank each time.
The alternative is to store the information once and let the form be filled from it. That is Filly's model: a reusable profile per person or client, applied to whatever PDF or Word form arrives, with a review step before export. Free covers 3 forms, 5 clients and 10 fills a month with no card, which is enough to test it against your real forms rather than a demo.
And if you are the one sending forms out, the loop inverts — you can prefill what you already know and send a link instead of an attachment, so the other person only fills the gaps and signs. That is sending someone a prefilled form to sign, and it removes the "fill it and email it back" step from their side entirely.
FAQ
Do I need to print, sign, and scan it?
Almost never in 2026. Typed entries plus a drawn or typed signature are accepted for the large majority of business and government forms, and a scan-back cycle degrades the file and loses the text layer. Print only when the recipient explicitly demands a wet signature.
The form arrived as a Word document, not a PDF. Same steps?
Broadly, but check whether it is a true fillable Word form or just a document with underscores. If it is the latter, typing into it reflows the layout and the result looks wrong. See filling a Word document that isn't fillable.
The filled PDF is too big to email. What now?
Size usually comes from scanned page images or an embedded signature photo, not from your text. Re-export at a lower image quality, or send a link instead of an attachment. Most mail systems still cap attachments around 20–25 MB.
How do I add a signature without a scanner?
Draw it with a trackpad or finger, or type your name in a script face — both are standard e-signature practice. What matters legally is intent and a record of the act, not that the mark looks handwritten. Our overview of e-signature platforms and the E-SIGN Act covers where that line sits.
How can I be sure the recipient will see my answers?
Reopen the saved file from your file manager — not from the app you filled it in — and check the values are there. If you flattened it, they are part of the page and will render anywhere. If you did not, this reopen test is your only real check.
Can I keep a copy of what I sent?
Keep the flattened file you attached, not the blank original. If you fill the same form for many people, keep the answers as structured data rather than as a folder of PDFs — that is what makes next year's version a review instead of a retype.