How does 'Zero-Server' processing work?
PDFSlim uses WebAssembly and modern browser APIs to process your files directly on your machine. When you upload a file, it stays in your browser's memory and is not sent to our servers.
Technical Knowledge Base
Common Questions.
Expert Answers.
Answers about our local-first architecture, privacy approach, and document workflows.
Privacy & Infrastructure
Do you store any history of my files?
No. We do not keep a database of your files. Temporary data is cleared when you close or refresh the page.
Is there a file size limit for local processing?
The main limit is your device's available memory. Large files often perform better than on upload-based tools because there is no network transfer.
Is PDFSlim really free?
Yes. Local processing keeps costs lower than upload-based tools, and advertising helps support the service.
Legal & Security Standards
Is my digital signature legally binding?
Electronic signatures may be valid in many jurisdictions, but you should confirm the exact requirements for your contract or region.
Will redacted text still appear in search?
Redaction should always be reviewed carefully before sharing a file. For sensitive work, verify the output instead of assuming a visual mask is enough.
Does password protection use current standards?
PDF protection can add a useful layer for sharing, but it should still be paired with good storage and document handling practices.
Can the accessibility checker fix my PDF automatically?
The checker is mainly for identifying issues. Many accessibility fixes still need to be made in the source document or with more specific editing steps.
Tool Capabilities
Can I merge protected files?
That depends on the file restrictions and whether you are authorized to work with them. In some cases, the file may need to be unlocked first.
Does dark mode permanently change my file?
The preview mode does not change the original file unless you intentionally export a new version.
What formats are supported for conversion?
PDFSlim focuses on practical PDF-related workflows such as Word, Excel, PowerPoint, images, HTML, and text extraction.
Can I extract specific page ranges from a PDF?
Yes. Splitting tools are meant to help you create smaller, more focused files from longer documents.
Still have a specific question?
Reach out if you need help with a workflow, a bug, or a tool that is not behaving as expected.