Software Alternatives & Startups

PDFSharp VS KeptPDF

Compare PDFSharp VS KeptPDF and see what are their differences

PDFSharp logo PDFSharp

Office & Productivity and Development

KeptPDF logo KeptPDF

Redact, edit, OCR, and sign PDFs entirely in your browser. The file never leaves your device. Free, no account needed.
Visit Website
  • PDFSharp Landing page
    Landing page //
    2023-06-05
  • KeptPDF Landing page
    Landing page //
    2026-08-22

KeptPDF is a PDF toolkit that runs entirely in your browser. Nothing uploads: every tool runs on your own device, so the document never touches a server.

What it does:

  • Redaction that auto-detects names, SSNs, phone numbers, addresses, and dates, then removes the underlying text instead of drawing a box over it. Every redacted file gets an audit certificate that anyone can verify.
  • OCR that makes scanned PDFs searchable, with on-device processing.
  • Sign, annotate, compare, organize, split, merge, compress, convert, watermark, Bates numbering, exhibit stamps, and more. About 25 tools in total.
  • A command line version runs the same redaction engine on your own servers for bulk work: scanning bureaus, litigation support teams, and records departments process thousands of PDFs in one pass.

Who it is for: law firms, accounting practices, clinics, and anyone who shares documents they cannot afford to leak.

The core tools are free with no sign-up. Works offline as an installable app.

PDFSharp

Pricing URL
-
$ Details
-
Release Date
-

KeptPDF

$ Details
freemium $29 / Monthly (Pro, 1 user)
Release Date
2026 May
Startup details
Country
United States
State
Tennessee
Founder(s)
John Whitworth

PDFSharp features and specs

  • Open Source
    PDFSharp is open source, allowing developers to use, modify, and contribute to the library freely.
  • No External Dependencies
    The library does not require any external dependencies or proprietary software, making it easy to integrate into projects.
  • Cross-Platform
    Supports multiple platforms, allowing it to run on Windows, Linux, and macOS without significant changes.
  • Document Creation
    Provides robust capabilities for creating PDFs from scratch, with support for various content types like text, images, and shapes.
  • Active Community
    Has an engaged user community and a good number of resources available online for learning and troubleshooting.

Possible disadvantages of PDFSharp

  • Limited Editing Capabilities
    PDFSharp excels at creating PDFs but has limited functionality when it comes to editing existing PDF files.
  • Performance Issues
    Some users report performance bottlenecks when dealing with very large PDF files due to its memory usage.
  • Lack of Advanced Features
    Does not support advanced PDF features like interactive forms, digital signatures, or encryption as extensively as some other libraries.
  • Sparse Documentation
    While basic documentation is available, more in-depth examples and advanced use cases might require additional research.

KeptPDF features and specs

  • Simple PDF Editing
    KeptPDF offers straightforward tools for editing, merging, splitting, and converting PDF files, making it accessible for users who need quick document management without a steep learning curve.
  • Web-Based Accessibility
    Being a web-based tool, KeptPDF can be accessed from any device with an internet connection, eliminating the need for software installation and allowing use across different operating systems.
  • Multiple File Format Support
    The platform supports conversion between PDF and various other file formats, offering flexibility for users who work with documents in different formats.
  • No Installation Required
    Since it operates in a browser, users can save storage space on their devices and avoid compatibility issues that sometimes arise with desktop software installations.
  • Quick Processing
    KeptPDF is designed to process PDF tasks efficiently, allowing users to complete common document tasks like compression or conversion in a relatively short amount of time.

Category Popularity

0-100% (relative to PDFSharp and KeptPDF)
PDF Tools
79 79%
21% 21
PDF
0 0%
100% 100
PDF Editor
100 100%
0% 0
PDF Readers And Editors
0 0%
100% 100

Questions & Answers

As answered by people managing PDFSharp and KeptPDF.

What makes your product unique?

KeptPDF's answer:

KeptPDF runs entirely in your browser. Your file, and the text inside it, never leaves your device. Not to an AI, not even to us. You can open your browser's network tab and watch: the document bytes never go out.

Most online PDF tools upload your file to a server first, and some "AI redaction" services quietly send your document text to a third-party model. That is the exact risk people are trying to avoid when they redact something.

KeptPDF also does true redaction. The text is removed from the file, not covered with a black box you can copy out later. Every redaction produces a verification certificate you can share with the file.

Why should a person choose your product over its competitors?

KeptPDF's answer:

Three reasons.

Privacy you can verify, not just a promise. Processing happens locally in the browser, so there is no upload step to trust. We do send anonymous usage counts for quota, and we say so plainly, but never your document.

Real redaction with proof. Removed text is permanently gone, and you get a certificate showing the file was checked for leftover extractable text. Automated detection cannot catch everything, so a final human review is still your job, and the tool says that too.

It works on a phone. Most PDF suites assume a desktop. KeptPDF was built and used on a phone first, so redacting a document while you are standing in a hallway actually works.

How would you describe the primary audience of your product?

KeptPDF's answer:

Anyone who has to hand a document to someone else and needs the sensitive parts gone first.

In practice that is solo attorneys and small law firms, accountants and tax preparers, healthcare and records staff handling requests, HR teams, and individuals dealing with their own medical, legal, or financial paperwork.

The common thread is not an industry. It is a person who cannot upload a confidential file to a random website, and who does not have an enterprise IT budget to solve it.

What's the story behind your product?

KeptPDF's answer:

A family member got seriously ill. We spent most days at the hospital, and straight answers were hard to come by, so we leaned on AI tools to make sense of the records, notes, and lab results.

But you cannot paste a medical record into an AI chat. You have to strip the names, the ID numbers, the diagnoses first. And almost every tool we found either wanted to upload the whole file to a server, or "auto-redacted" by sending the document text to an online AI. That was the exact thing we were trying to avoid.

Most of this was happening on a phone, at a bedside. So I built the tool I needed: redaction that runs on the device, works on mobile, and never sends the file anywhere. That turned into KeptPDF, which is now a full PDF suite with over 20 tools, all local-first.

Which are the primary technologies used for building your product?

KeptPDF's answer:

The app is plain JavaScript with no front-end framework, which keeps it fast and keeps the code auditable.

PDF work happens in the browser using pdf.js for rendering and pdf-lib for writing. Text recognition uses Tesseract running as WebAssembly. Password and encryption handling uses a WebAssembly build of qpdf. It is a Progressive Web App, so it installs and works offline.

The thin server side is Node on Vercel, with Postgres for accounts, Stripe for billing, and Resend for email. None of those ever see a document.

Who are some of the biggest customers of your product?

KeptPDF's answer:

KeptPDF is early and independent, and we do not publish customer names. The product is privacy-first by design: we never see your documents, and we do not track who our users are or what they work on. Publishing a client list would sit badly next to that.

The user base today is mostly solo attorneys, small firms, accountants, and individuals handling their own records.

User comments

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Reviews

These are some of the external sources and on-site user reviews we've used to compare PDFSharp and KeptPDF

PDFSharp Reviews

2024 Best C#/ .NET PDF Library for Developers
PDFSharp is an open source .NET library that easily processes PDF documents under Windows, Linux, Mac, and all other .NET platforms. It supports most fundamental PDF features, such as creating new PDF documents, and modifying, merging, and splitting existing PDF files. With it, developers can use just one source code for drawing on a PDF page as well as in a window or on the...
Source: www.compdf.com

KeptPDF Reviews

We have no reviews of KeptPDF yet.
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What are some alternatives?

When comparing PDFSharp and KeptPDF, you can also consider the following products

Smallpdf - PDF document management and conversion suite

iTextPDF - iText offers flexible tools for PDF creation, editing and inspection.

iLovePDF - Premium online PDF tool set

Sejda - Split, merge and other powerful PDF tools.

PDF24 PDF Creator - Create PDF and convert documents to PDF for free with the free PDF24 PDF Creator.

Adobe Acrobat DC - Make your job easier with Adobe Acrobat DC, the trusted PDF creator. Use Acrobat to convert, edit and sign PDF files at your desk or on the go.