Detect and fill interactive PDF form fields — text inputs, checkboxes, dropdowns, and radio buttons. All processing happens in your browser.
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Detecting form fields...
Detect and complete interactive PDF form fields in three simple steps — no software installation required.
Drag and drop your PDF form into the upload area, or click "Choose PDF File" to browse your device. The tool accepts any PDF document and automatically scans it for interactive form fields including text inputs, checkboxes, dropdown menus, and radio button groups. Within seconds you will see every detected field listed and ready to fill.
Each detected form field is rendered as an editable input labeled with its original PDF field name. Type text into text fields, check or uncheck boxes, select options from dropdowns, and choose radio button values. All fields are displayed in a scrollable panel so you can work through even the longest forms efficiently. Optionally enable "Flatten form" to lock values permanently.
Click "Fill & Download" and your completed PDF form is saved to your device in seconds. All field values are written directly into the PDF using pdf-lib. If you chose to flatten the form, the fields become permanent page content that cannot be further edited. Your original PDF file is never modified — the tool creates a brand-new file with your responses.
A faster, safer, and more convenient way to fill PDF forms — built for everyone.
There is no premium tier, no usage cap, and no hidden paywall. ConvertKr's PDF form filler is free for everyone, whether you need to fill a single application form or process a batch of government documents. Essential file tools should be accessible without a subscription or per-file charge.
Unlike most online PDF tools, your files never leave your device. All form detection and filling happens locally in your browser using JavaScript and the pdf-lib library. There is no server upload, no temporary cloud storage, and no risk of your personal information or confidential data being accessed by anyone else.
The tool automatically detects all interactive form fields embedded in the PDF — text fields, checkboxes, radio buttons, dropdown menus, and option lists. No manual configuration needed; just upload and start filling. Each field is labeled with its original name from the PDF form definition.
Whether your PDF form contains simple text inputs, multi-line text areas, checkboxes, radio button groups, single-select dropdowns, or multi-select option lists, the tool handles them all. Each field type is rendered as its native HTML equivalent for a familiar and intuitive editing experience.
Choose to flatten the form after filling to permanently embed all values into the page content. Flattened forms cannot be further edited, making them ideal for final submissions. Leave the option unchecked if you want recipients to be able to modify the values later.
ConvertKr never adds its own watermarks, logos, or branding to your output files. Your downloaded filled PDF is clean, professional, and ready to submit to employers, government agencies, schools, or clients without any third-party marks.
Everything you need to know about working with interactive PDF form fields.
What Are PDF Form Fields? PDF forms are documents that contain interactive fields designed to collect information from the reader. Unlike static PDFs where text is fixed on the page, fillable PDFs include designated areas where users can type text, select options, check boxes, and make choices. These forms are widely used in government applications, tax filings, insurance claims, employment paperwork, academic registrations, medical intake forms, and countless other scenarios where structured data collection is needed. The form fields are defined within the PDF specification and can be read and written programmatically, which is exactly what this tool does using the pdf-lib JavaScript library.
Understanding Field Types PDF forms support several distinct field types, each designed for a specific kind of input. Text fields accept free-form text and may be single-line or multi-line. Checkboxes represent yes/no or true/false choices and can be independently toggled. Radio buttons are grouped so that selecting one option automatically deselects the others in the same group, useful for mutually exclusive choices like gender or payment method. Dropdowns present a list of predefined options where the user selects exactly one. Option lists are similar to dropdowns but allow multiple selections. This tool detects all of these types and renders the appropriate HTML input for each one.
When to Flatten a Form Flattening a PDF form means converting all interactive fields into static page content. The field values become regular text drawn on the page, and the form layer is removed entirely. Flatten your form when you are making a final submission and want to ensure no one can alter your responses — for example, when filing a signed contract, submitting a completed tax form, or sending a finished application. Do not flatten if the recipient needs to make corrections or if the form will be processed by software that reads field values programmatically. When in doubt, download both versions: one flattened for archival and one editable for future revisions.
Technical Details and Compatibility ConvertKr's PDF form filler uses the pdf-lib JavaScript library to read the PDF's AcroForm dictionary, enumerate all field objects, and set their values according to your input. The library writes values using the correct PDF operators for each field type, ensuring maximum compatibility with Adobe Acrobat, Preview, Chrome's built-in viewer, and every other major PDF reader. Because all processing runs in your browser, there is zero server interaction — your PDF and the data you enter remain entirely on your device. The output file is a fully valid PDF that works in every reader, printer, and archival system.
Everything you need to know about filling PDF forms with ConvertKr.
The tool supports all standard interactive PDF form field types: text fields (single and multi-line), checkboxes, radio button groups, dropdown menus (single select), and option lists (multi-select). Each field is automatically detected and rendered as its corresponding HTML input element so you can fill it naturally.
If the tool scans your PDF and finds no interactive form fields, it will display a clear message letting you know. Many PDFs are static documents without a form layer. In that case, you can use ConvertKr's PDF Editor to type text directly onto the pages, add annotations, or place signatures.
Flattening permanently converts all interactive form fields into static page content. Your filled-in values become regular text on the page, and the editable fields are removed. This is useful when you want to lock your answers and prevent anyone from changing them. If you leave the flatten option unchecked, the form fields remain editable in the downloaded PDF.
Absolutely. All form detection and filling happens entirely in your browser using JavaScript and the pdf-lib library. Your files are never uploaded to any server, and we cannot see, access, or store your documents or the personal information you enter. Once you close the browser tab, all data is gone.
Yes. After downloading your filled PDF, click the Reset button to clear all fields and start over with the same form, or upload the original PDF again. You can fill and download as many copies as you need with different values — there is no limit on the number of times you can use the tool.
Yes. The tool uses pdf-lib to write field values using standard PDF operators, ensuring full compatibility with Adobe Acrobat, Adobe Reader, macOS Preview, Chrome's built-in PDF viewer, Firefox, and all other major PDF readers. Flattened forms are also fully compatible since the values become regular page content.
ConvertKr does not impose artificial limits on file size or the number of form fields. Since processing runs locally in your browser, the practical ceiling depends on your device's available memory. Most modern devices handle complex forms with hundreds of fields without any issues.
Yes. ConvertKr runs entirely in your web browser, so it works on smartphones and tablets just as well as on desktop computers. There is nothing to install — if your device has a modern browser with JavaScript enabled, you can fill PDF forms on the go. The interface is fully responsive and optimized for touch screens on iOS and Android.
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