Add documentation for all PDF tools

docs/tools/rtf-to-pdf.md

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+---
+title: RTF to PDF
+description: Convert Rich Text Format (RTF) files to PDF in your browser using a LibreOffice-powered engine.
+---
+
+# RTF to PDF
+
+Convert Rich Text Format documents to PDF. RTF is a cross-platform document format supported by virtually every word processor. This tool uses a browser-based LibreOffice engine to render RTF files with their formatting intact -- bold, italic, tables, and embedded images all carry over to the PDF.
+
+## Supported Formats
+
+| Format | Extensions | MIME Types                    |
+| :----- | :--------- | :---------------------------- |
+| RTF    | `.rtf`     | `text/rtf`, `application/rtf` |
+
+## How It Works
+
+1. Click the upload area or drag and drop one or more RTF files.
+2. Review the file list. Add more or remove files as needed.
+3. Click **Convert to PDF**. The LibreOffice engine initializes on first use, then processes each file.
+4. A single file downloads directly as a PDF. Multiple files are delivered as `rtf-converted.zip`.
+
+## Options
+
+This tool has no additional settings. The conversion preserves the original RTF formatting.
+
+## Output
+
+| Input Count | Output                                                        |
+| :---------- | :------------------------------------------------------------ |
+| 1 file      | Single PDF download (e.g., `letter.pdf`)                      |
+| 2+ files    | ZIP archive (`rtf-converted.zip`) containing one PDF per file |
+
+## Use Cases
+
+- Converting legacy RTF documents from older word processors to modern PDFs
+- Turning RTF email templates into PDF previews
+- Processing RTF output from legal or medical software systems
+- Batch converting RTF files from a document management system to PDF for archival
+
+## Tips
+
+- The LibreOffice engine is loaded once and cached. The first conversion in a session takes a few extra seconds; subsequent ones are faster.
+- RTF files with embedded OLE objects may not render all objects perfectly. Plain text, images, and standard formatting convert reliably.
+- If your RTF files were created by Microsoft Word, you can also convert them directly with the [Word to PDF](./word-to-pdf) tool, which accepts RTF alongside DOC and DOCX.
+
+## Related Tools
+
+- [Word to PDF](./word-to-pdf)
+- [ODT to PDF](./odt-to-pdf)
+- [Text to PDF](./txt-to-pdf)