PDF form filling

Five kinds are detected automatically: single-line text, multi-line text, checkboxes, radio button groups, dropdowns (single choice) and list boxes (multiple choice). Values already in the file are prefilled, required fields are marked, read-only fields are disabled and never written back, and fields this tool does not handle - signature and button fields - are listed separately with a note to handle them in a PDF reader. If the PDF has no form fields at all (many are merely drawn to look like one), the page says so plainly and points you to the PDF metadata, PDF extraction and page manager tools instead.

pdf-lib uses the PDF built-in standard fonts, which can only encode the WinAnsi character set - English, digits, Western European letters and common punctuation. Chinese, Japanese, Korean, circled numbers like ① and emoji trigger an error like WinAnsi cannot encode (0x4e2d) when the form appearance is refreshed, and this tool does not fail silently: before exporting it scans and tells you exactly which field and which character fails. The fixes: switch the content to letters/digits, or fill this PDF in Adobe Acrobat, WPS or a similar reader that ships Chinese fonts. This tool deliberately does not bundle a Chinese font - it would inflate the page from a few hundred kilobytes to tens of megabytes.

Keep editable: the exported PDF still contains the form fields - other people can keep editing it, and you can re-fill it here. Flatten: the entered content is painted into the page as fixed content and the form fields are removed from the file - whoever receives it cannot change it anymore, which suits formal submission and print archiving, and also keeps others from reading your raw field values. Either way you get a new file and your original is never modified; if you need changes after flattening, re-fill the original file.

No upload. Parsing, filling, flattening and exporting all run in your browser with pdf-lib - the file never leaves your machine and reloading the page clears everything. Password-protected (encrypted) PDFs cannot be parsed in the browser; the page will ask you to open it in a reader, enter the password and save an unencrypted copy to bring back here - this tool does not decrypt and does not remove passwords. Form fields are part of the original PDF: the exported file keeps everything else the original contained.