Add documentation for all PDF tools

docs/tools/pdf-multi-tool.md

@@ -0,0 +1,52 @@
+---
+title: PDF Multi Tool
+description: An all-in-one page manager for merging, splitting, rotating, duplicating, deleting, and reordering PDF pages.
+---
+
+# PDF Multi Tool
+
+A unified workspace for every page-level PDF operation. Upload one or more PDFs and work with all their pages in a single visual grid. Rotate, reorder, duplicate, delete, insert new PDFs, add blank pages, and split the result -- all without leaving the tool.
+
+## How It Works
+
+1. Click **Upload PDFs** or drag files onto the upload area. Multiple files are supported.
+2. All pages from every uploaded file appear in a scrollable grid with thumbnails.
+3. Use the toolbar or per-page action buttons to manipulate pages.
+4. Select pages using the checkbox on each card, then apply bulk operations.
+5. Mark split points with the scissors icon to divide the output into separate files.
+6. Click **Export PDF** to download the final result. If split markers are present, the output is a ZIP of multiple PDFs.
+
+## Features
+
+- **Merge**: Upload multiple PDFs and they combine into one workspace automatically
+- **Reorder**: Drag and drop page cards to rearrange the sequence
+- **Rotate**: Per-page or bulk rotation in 90-degree increments (left or right)
+- **Duplicate**: Clone any page with one click
+- **Delete**: Remove individual pages or bulk-delete selected ones
+- **Insert PDF**: Add a new PDF after any specific page
+- **Add Blank Page**: Append a blank A4 page at the end
+- **Split**: Place split markers between pages, then export as a ZIP of separate PDFs
+- **Select All / Deselect All**: Quick selection for bulk operations
+- **Undo / Redo**: Full undo/redo history for every operation
+- **Download selected**: Export only the selected pages as a standalone PDF
+- Auto-repairs corrupted PDFs before loading
+
+## Use Cases
+
+- Building a custom document from pages across multiple source PDFs
+- Cleaning up a scanned document by deleting blank pages, rotating sideways scans, and reordering sections
+- Splitting a large PDF at chapter boundaries using visual split markers
+- Quick page-level editing without needing a full PDF editor
+
+## Tips
+
+- The undo/redo system tracks every operation. Use it freely -- you cannot accidentally destroy your work.
+- Split markers appear as dashed blue lines between pages. Place them visually where you want the document divided, then export to get a ZIP.
+- For simple merge or split tasks, the dedicated [Merge PDF](./merge-pdf) or [Split PDF](./split-pdf) tools may be faster. The Multi Tool shines when you need multiple operations in one session.
+
+## Related Tools
+
+- [Merge PDF](./merge-pdf)
+- [Split PDF](./split-pdf)
+- [Organize & Duplicate](./organize-pdf)
+- [Rotate PDF](./rotate-pdf)