PDF Form Filler
PDF Form Filler
Drag & drop your PDF here
or click to browse
Supports AcroForm PDFs — files are processed locally
Upload a PDF to Get Started
Drag and drop a PDF form onto the upload area, or click to browse. All fillable fields will be detected automatically — no account required.
Fill AcroForm fields instantly — 100% private, 100% free, no account needed
Filling out PDF forms has long been one of the most frustrating tasks in everyday digital life. Whether you need to complete a government application, an employment form, a medical intake document, a lease agreement, or a tax worksheet, PDF forms are everywhere — and yet most people struggle to fill them without downloading expensive software or uploading sensitive documents to unknown servers. Our free PDF Form Filler solves all of these problems at once by processing everything directly inside your browser using the open-source pdf-lib library. Your PDF file never leaves your device, is never uploaded to any server, and is never stored anywhere outside your own computer. The tool works with any PDF that contains AcroForm fields — the standard interactive form fields built into the PDF specification. When you upload or drag and drop a PDF file, the tool automatically scans the document and detects every fillable field: text boxes, checkboxes, radio button groups, dropdown menus, and option lists. Each field is presented in a clear, organized list with a type icon so you always know what kind of input is expected. You can fill them one by one or use the JSON import feature to pre-fill a large form from a saved data file in seconds. Once you have filled the fields, you can download the completed PDF with a single click. You can choose to keep the form interactive — so the recipient can still edit field values — or flatten the form, which converts all the AcroForm fields into static PDF content that cannot be changed. Flattening is the right choice when you want to submit a final, tamper-resistant version of a document. If you are filling a recurring form — such as a weekly timesheet or a monthly expense report — the JSON export and import features let you save your field values and reload them next time, eliminating repetitive data entry. Privacy is the cornerstone of this tool. Unlike most competing services, there is absolutely no server-side processing. The pdf-lib library runs entirely in your browser's JavaScript engine, which means your personal details, financial data, health information, and legal documents never travel over the internet during processing. This makes the tool suitable for HIPAA-sensitive healthcare forms, GDPR-regulated personal data, confidential legal agreements, and any other document where data security matters. You do not need to create an account, verify your email address, or accept any terms that involve data processing on remote servers. For developers and power users, the tool offers a JSON export of all field names and values, which is useful for understanding the AcroForm structure of a PDF or for building automation scripts that use pdf-lib. Knowing the exact field names programmatically is one of the most common developer challenges when working with PDF forms, and this tool surfaces that information with one click. The fill progress bar at the top of the field list makes it easy to see at a glance whether you have completed all required fields before downloading — a simple but genuinely useful feature that most competitors overlook. The tool supports all major AcroForm field types defined in the PDF specification: PDFTextField (single-line and multi-line text input), PDFCheckBox (boolean on/off fields), PDFRadioGroup (mutually exclusive radio button selections), PDFDropdown (single-selection drop-down lists), and PDFOptionList (scrollable option lists). Each field type renders with an appropriate native HTML control — text inputs for text fields, checkboxes for boolean fields, radio groups for radio fields, and native select menus for dropdown and option lists — ensuring maximum compatibility across all modern browsers including Chrome, Firefox, Safari, and Edge on desktop and mobile. Whether you are a student filling out a scholarship application, a small business owner completing a vendor form, a healthcare professional handling patient intake documents, or a developer building a PDF automation workflow, this tool is designed to make the process fast, private, and completely free.
Understanding PDF Form Filling
What Is an AcroForm?
An AcroForm is the official name for the interactive form layer built into the PDF file format, standardized by Adobe in PDF 1.2 and now governed by the ISO 32000 specification. AcroForms consist of widget annotations embedded in a PDF document that define fillable fields — text boxes, checkboxes, radio buttons, dropdowns, and list boxes. When a PDF with AcroForm fields is opened in a compatible viewer such as Adobe Acrobat or this tool, the viewer renders each widget as an interactive HTML-like control. The field values are stored in the PDF's internal dictionary structure and can be read, written, and exported programmatically. Not all PDFs have AcroForms — scanned documents and flat PDFs created by printing to PDF are just images of pages with no embedded field data. This tool works exclusively with true AcroForm PDFs; flat PDFs will show zero detected fields.
How Does PDF-lib Process Fields?
This tool uses pdf-lib, a modern TypeScript library for creating and modifying PDF documents in the browser without any server-side code. When you upload a PDF, the tool reads it as an ArrayBuffer and passes it to PDFDocument.load(). The library then parses the PDF's internal cross-reference table, locates the AcroForm dictionary, and enumerates all field widgets. For each field, pdf-lib returns a typed object — PDFTextField, PDFCheckBox, PDFRadioGroup, PDFDropdown, or PDFOptionList — that exposes methods for reading and writing the field's value. When you click Download, the tool writes all current field values back into these objects, optionally calls form.flatten() to rasterize the fields into static content, and then serializes the entire document to a new byte array using pdfDoc.save(). The result is downloaded as a standard PDF file with no modifications beyond what you explicitly entered.
Why Privacy Matters for PDF Forms
PDF forms routinely contain some of the most sensitive information people handle: Social Security numbers, bank account details, medical histories, legal agreements, salary information, and government-issued identification numbers. When you upload a form to a cloud-based PDF editor, that data travels to a remote server where it may be stored in logs, used to train AI models, shared with third-party analytics, or potentially exposed in a data breach. Many free online PDF tools monetize through data harvesting — the service is free because your document content is the product. This browser-based tool eliminates that risk entirely by processing everything locally. The pdf-lib library runs inside your browser's sandboxed JavaScript environment; the PDF bytes are loaded into browser memory and the filled document is generated there too. No network request is made for your file at any point.
Limitations to Be Aware Of
While this tool handles the vast majority of real-world PDF forms, there are some limitations to understand. Password-protected or encrypted PDFs cannot be fully processed — pdf-lib will attempt to load them with the ignoreEncryption option, but the field data may be inaccessible or unwritable; in this case the tool will show a clear error message. PDFs with XFA forms (an older Adobe proprietary format used in some government and enterprise documents) are not supported — XFA is a different form technology that pdf-lib does not currently implement. Very large PDFs (over 50–100 MB) may be slow to process or may exhaust available browser memory depending on your device. Signature fields are detected but cannot be signed with a cryptographic signature in this tool — you will need dedicated e-signature software for legally binding digital signatures. Finally, some PDFs embed custom fonts or JavaScript that governs field behavior; these scripts do not execute in pdf-lib, so calculated fields or field validation rules defined in JavaScript will not run.
How to Fill a PDF Form
Upload Your PDF
Drag and drop your PDF form onto the upload area, or click the zone to open a file picker. The tool supports any PDF with AcroForm fields — the standard interactive form format used in government, legal, HR, and medical documents.
Fill in the Detected Fields
After the PDF loads, every fillable field is listed automatically with its name, type icon, and current value. Type into text fields, toggle checkboxes, select radio options, or choose from dropdown menus. The progress bar at the top tracks how many fields you have completed.
Choose Your Download Options
Set your desired output filename. Toggle 'Flatten form on download' if you want the finished PDF to be non-editable — ideal for final submissions. Use 'Export Fields (JSON)' to save your field values for reuse next time with 'Import Fields (JSON)'.
Download the Filled PDF
Click 'Download Filled PDF' in either the input panel or the results panel. The tool writes all your values into the PDF using pdf-lib, optionally flattens the form, and triggers an immediate browser download — all without any server connection.
Frequently Asked Questions
Are my PDF files uploaded to a server?
No — your PDF never leaves your device. This tool uses pdf-lib, a JavaScript library that runs entirely inside your browser. When you load a PDF, it is read into your browser's memory using the FileReader API. All field detection, value writing, and PDF generation happen locally on your device. No network request is made for your file content. This makes the tool safe for sensitive documents including medical forms, tax documents, financial applications, and legal agreements. You can confirm this by opening your browser's developer tools and inspecting the Network tab — you will see zero upload requests for your PDF data.
Why does the tool show zero fields for my PDF?
There are two common reasons. First, the PDF may be a flat document — created by scanning a paper form and saving it as an image-based PDF, or by printing a digital document to PDF without preserving form fields. These documents look like forms but have no embedded AcroForm data. To fill a flat PDF, you would need annotation or overlay tools rather than a form filler. Second, the PDF may use XFA forms, which is an older Adobe proprietary format incompatible with pdf-lib. XFA is still used by some government agencies (particularly in the US and EU). If your PDF came from an official government source and has zero fields here, try opening it in Adobe Acrobat Reader first to check whether it is XFA-based.
Can I save my form data and reload it later?
Yes. Use the 'Export Fields (JSON)' button to download a JSON file containing all field names and their current values. This file is plain text and can be opened in any text editor. Next time you load the same PDF form — or a structurally identical one — click 'Import Fields (JSON)' and select your saved file. The tool will match field names and pre-fill all matching values automatically. This is especially useful for recurring forms like weekly timesheets, monthly expense reports, or standard business contracts where the field structure stays the same but the values change periodically.
What does 'Flatten form on download' mean?
Flattening converts all AcroForm interactive widgets into static visual content embedded in the PDF page. After flattening, the PDF looks the same visually but no longer contains interactive form fields — the values you entered become regular text or graphics on the page. A flattened PDF cannot be edited further using form-filling tools. This is the right choice when you are submitting a final document and want to ensure the recipient cannot change the values. If you leave flattening off, the downloaded PDF retains interactive AcroForm fields and the recipient can continue editing the values in any PDF viewer that supports forms.
What happens with password-protected PDFs?
pdf-lib has limited support for encrypted PDFs. The tool attempts to load the file using the ignoreEncryption option, which sometimes allows reading the structure of an encrypted document. However, password-protected PDFs that use standard PDF encryption will typically fail to load or will load without accessible field data because the content streams are encrypted with the owner password. In this case the tool displays a clear error message. The solution is to use Adobe Acrobat or another trusted PDF tool to remove the password protection first (you will need to know the password to do this), and then re-upload the unlocked PDF here.
Is this tool free? Are there file size limits or field count limits?
Yes, this tool is completely free with no account required, no watermarks on downloaded PDFs, and no imposed file size limit from a server side. Since processing happens in your browser, the practical limit is your device's available RAM. Modern devices typically handle PDFs up to 50–100 MB without difficulty. Very large PDFs with hundreds of high-resolution images may be slow to process or may cause the browser tab to run out of memory. There is no limit on the number of fields — the tool processes every AcroForm field in the document regardless of count.