What Is PDF Form Builder?
PDF Form Builder lets you create interactive, fillable PDF forms from scratch. Add text fields, checkboxes, dropdowns, radio buttons and signature boxes to build professional intake forms, applications, surveys, and questionnaires — all in the browser.
How to Use This Tool
Start with a blank form or upload an existing PDF as a template. Pick a field type, tap the page to place it, then drag to move it or pull the corner to resize. Give each field a name, a default value, and required or read-only flags. When finished, export the fillable PDF. Everything runs client-side — no data is uploaded.
Why Use PDF Form Builder?
Creating fillable PDFs normally requires Adobe Acrobat Pro or similar paid software. This tool covers the basic job of adding fields to a page for free, with no account needed and complete privacy for any sensitive form templates you create. For a detailed walkthrough, see our step-by-step guide.
Worked example: a seven-field client intake form
We built a one-page intake form with the same pdf-lib calls this tool makes on export, then opened the file with a separate PDF library (pypdf 5.9) to see exactly what a PDF reader receives. The finished form was 7,066 bytes.
| Field | Set up in the tool as | Written to the PDF as | Field flags (Ff) |
|---|
| Full name | Text, required | /FT /Tx | Ff 2: Required (bit 2) |
| Email | Text, required | /FT /Tx | Ff 2: Required |
| Project details | Text, multi-line | /FT /Tx | Ff 4096: Multiline (bit 13) |
| Budget | Dropdown, 3 options | /FT /Ch with an /Opt list | Ff 131072: Combo (bit 18) |
| Contact preference | Radio group: Email, Phone | /FT /Btn | Ff 32768: Radio (bit 16) |
| Agree to terms | Checkbox, required | /FT /Btn | Ff 2: Required |
| Signature | Signature box | /FT /Tx (plain text) | None. It is a typed-name box, not a /Sig signature field |
Two things follow from the specification. First, the Required flag is defined for export by a submit-form action (ISO 32000-1, Table 221), so a reader will not stop someone saving or emailing the form with a required field empty; Acrobat can outline required fields, other viewers may not show them at all. If a field really must be filled, say so in its label. Second, the signature box is ordinary text, so a typed name is all it holds; for a drawn signature on the completed form, use the PDF Signer.
Sources, checked October 11, 2026: ISO 32000-1:2008 (PDF 1.7), §12.7.3-12.7.4, Tables 221, 226, 228 and 230; pdf-lib documentation.
Frequently Asked Questions
What is a fillable PDF form and how is it different from a regular PDF?+
A fillable PDF contains AcroForm fields (text boxes, checkboxes, radio buttons and dropdowns) that people can click into and complete in a PDF reader. A regular PDF is flat: recipients have to print it, write on it and scan it back. This tool adds real AcroForm fields to a flat PDF or to a blank page. AcroForm is the form format that Adobe Acrobat Reader, Apple Preview and the Chrome and Firefox PDF viewers fill; some phone apps support fewer field features, so test your form in the app your recipients use.
Is my PDF uploaded to a server?+
No. Your PDF never leaves your device. Everything happens locally in your browser using pdf-lib — the fields are added, the file is modified, and the download is generated entirely client-side. There are no uploads, no tracking of file contents, and no account or login required.
Which field types can I add?+
Single-line and multi-line text fields, checkboxes, radio button groups, dropdowns and signature boxes. A signature box is a text field sized for a typed name; it is not a digital-signature field. Place a field by tapping the page, then drag it, resize it from its corner or type exact width and height. Radio buttons that share a name form one group, so choosing one clears the others, and each gets its own value.
Will the resulting PDF work in Adobe Acrobat and mobile PDF readers?+
The fields are standard AcroForm fields written by pdf-lib with appearance streams, which is what Acrobat Reader, Preview and browser PDF viewers fill. We checked our output with qpdf (no structural errors) and pypdf (every field reads and fills). Mobile apps vary in which field features they support, so open the form on the device your recipients use before sending it widely. If a reader cannot fill the form, our PDF Form Filler can fill the fields instead.
Can I send the fillable PDF to others to complete?+
Yes. The download is a fillable PDF you can email or share. Recipients open it in a PDF reader, fill the fields and save or print the result. To add a drawn signature, use our PDF Signer. To lock a filled form against further edits, use our PDF Flattener.
How does this compare to Adobe Acrobat Pro's 'Prepare Form' feature?+
Acrobat Pro's Prepare Form can detect fields automatically and supports calculations, validation scripts, conditional logic and digital-signature fields, and it needs a paid Acrobat subscription. This tool does none of those. It places basic fields by hand, free and without uploading your file. For a simple intake form, application or waiver that is often enough; for calculated or validated forms, use Acrobat or a similar editor.
What types of form fields does the builder support?+
Text fields (single or multi-line), checkboxes, radio button groups, dropdowns and signature boxes. Each field gets the name you type (a repeated name gets _2, _3), plus optional settings: default text for text fields, a default choice for dropdowns, checked or selected by default for checkboxes and radio buttons, required and read-only. Validation patterns and calculations are not supported.
Will the forms work for clients who fill them out and email back?+
Yes. After filling, people save the PDF from their reader and email it back; the answers are stored in the PDF's AcroForm fields. Because each field keeps the name you gave it, a script can read the answers by name: our test output read and filled correctly with pypdf, a common Python PDF library.
Built by Derek Giordano · Part of Ultimate Design Tools
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