Add documentation for all PDF tools

docs/tools/divide-pages.md

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+---
+title: Divide Pages
+description: Split PDF pages horizontally or vertically into smaller sub-pages.
+---
+
+# Divide Pages
+
+Cut individual PDF pages into halves by splitting them horizontally or vertically. This is useful when a single page contains content that should be separated into distinct pages -- for example, a two-column layout scanned as one wide page.
+
+## How It Works
+
+1. Upload a PDF file.
+2. Select the split direction: **Vertical** (left/right halves) or **Horizontal** (top/bottom halves).
+3. Optionally specify a page range to limit which pages get divided. Leave blank to divide all pages.
+4. Click the process button to generate the divided PDF.
+
+## Features
+
+- Vertical split: divides each page into left and right halves
+- Horizontal split: divides each page into top and bottom halves
+- Page range filter to selectively divide specific pages
+- Non-targeted pages pass through unchanged
+- Preserves content quality without re-rendering
+
+## Use Cases
+
+- Separating two-up scanned pages (e.g., a book scan with left and right pages on one sheet)
+- Splitting a landscape PDF with side-by-side content into individual portrait pages
+- Dividing tall infographics or posters into separate top and bottom sections
+- Preparing wide-format documents for standard paper printing
+
+## Tips
+
+- If your pages have unequal content distribution, the split still happens at the exact midpoint. For asymmetric splits, consider [Crop PDF](./crop-pdf) instead.
+- Combine this tool with [Rotate PDF](./rotate-pdf) if your pages need rotation before or after dividing.
+
+## Related Tools
+
+- [Split PDF](./split-pdf)
+- [Crop PDF](./crop-pdf)
+- [N-Up PDF](./n-up-pdf)
+- [Posterize PDF](./posterize-pdf)