どのようにお手伝いできますか？

Yes! Core PDF tools are free to start with 3 tasks per day. We believe basic PDF tools should be accessible to everyone. We offer premium features through SafeRedact for users who need AI-powered redaction.

No. ModernPDF uses zero-knowledge processing, meaning all PDF processing happens entirely in your browser using JavaScript. Your files never leave your device and never touch our servers. We couldn't see your files even if we wanted to.

You can verify this yourself: open your browser's Developer Tools (F12), go to the Network tab, and process a file. You'll see no file uploads—only static assets loading.

No. Since your files never leave your device, we have no way to recover them. Make sure to download your processed files before closing the browser tab. We recommend keeping backups of important documents.

Yes! Once you've loaded a tool page, it works entirely offline. The JavaScript runs locally in your browser with no server communication required. This is another benefit of our zero-knowledge architecture.

ModernPDF works on all modern browsers including:

• Google Chrome (recommended)
• Mozilla Firefox
• Apple Safari
• Microsoft Edge

We recommend using the latest version of your browser for the best experience. Some features may be limited on mobile browsers due to memory constraints.

SafeRedact is our premium AI-powered redaction tool. While ModernPDF's free redact tool requires you to manually draw boxes, SafeRedact uses AI to automatically detect and highlight sensitive information like:

• Names and personal identifiers
• Social Security Numbers
• Phone numbers and emails
• Addresses and locations
• Financial information

You just review and approve the suggestions, making redaction much faster for large documents.

This can happen if your PDF is already highly optimized or uses efficient compression. Our compressor works best on PDFs with:

• Large embedded images
• Redundant data or fonts
• Inefficient encoding from older software

Try a higher compression level, or your file may already be as small as possible.

Yes. ModernPDF's redaction tool converts pages to images (rasterization), completely destroying the original text layer. Redacted content cannot be recovered, copied, or searched. This is true redaction, not just visual covering.

Learn more about why this matters in our Complete Guide to PDF Privacy.

OCR accuracy depends on several factors:

• Image quality — Higher resolution scans work better
• Contrast — Clear black text on white background is ideal
• Language — Make sure the correct language is selected
• Font style — Handwriting and unusual fonts are harder to recognize
• Skew — Straighten crooked scans before processing

Try these troubleshooting steps:

1. Refresh the page and try again
2. Make sure JavaScript is enabled in your browser
3. Try a different browser (Chrome recommended)
4. Check if the PDF is password-protected
5. For very large files (100MB+), try splitting first
6. The PDF may be corrupted — try opening it in Adobe Reader first

Since processing happens in your browser, the limit depends on your device's available memory rather than a fixed limit we impose. In practice:

• Desktop: Files up to 100-200MB typically work well
• Mobile: Recommend staying under 20-50MB
• Very large files: Consider splitting into smaller parts first

If your browser becomes slow or unresponsive, the file may be too large for your device's memory.

Files are merged in the order they appear in the list. Before merging:

• Check the file order in the upload area
• Drag and drop files to rearrange them
• The first file in the list will be first in the merged PDF