About PaperKit

What we do

PaperKit is a collection of small utilities for the jobs people do with PDFs and spreadsheets every week: signing and filling in PDFs, redacting private details, joining, splitting, rotating and compressing PDFs, turning images into PDFs, converting between CSV, Excel and JSON, and removing duplicate rows. Each one runs in your browser, so the file you pick is processed on your own device.

Why it works this way

Uploading a document to an unknown server is a real privacy risk, and it is slow for large files. Modern browsers are powerful enough to do the work locally, so we ship the tool to you instead of asking for your file. After the page has loaded, no network connection is needed to process a file.

Who makes it

PaperKit is part of the Numbers Plainly family of free tools, built and maintained by a small independent team. Each tool is tested against real files before release, and corrections are welcome by email.

How we build it

PDF editing uses pdf-lib (MIT licence), page drawing and text extraction use pdf.js (Apache-2.0) and ZIP files use fflate (MIT). Excel reading and writing is a compact implementation of the .xlsx format written for this site, covered by automated tests that round-trip data, dates, accents and large sheets. Heavy work runs in a Web Worker so the page stays responsive.

Limits you should know about

• Password-protected PDFs and legacy .xls workbooks must be converted first.
• Browser-only PDF compression re-draws pages as pictures, which suits scans better than text documents.
• Spreadsheet conversion keeps values, not formulas, styling, charts or macros.
• Signatures made here are simple electronic signatures (an image or drawing on the page), not certificate-based digital signatures.

How the site is funded

The site is free to use and may be supported by advertising. Ads are clearly labelled and are never placed next to upload or download buttons.

Spotted a bug or want a new tool? Get in touch. Read the Privacy Policy for details.