More details on partitioning strategy routing logic for files and pages (#701)

Author: Paul-Cornell

snippets/general-shared-text/platform-partitioning-strategies.mdx

@@ -8,4 +8,12 @@ including reduction in transformation quality.
 
 - **VLM**: For the highest-quality transformation of these file types: `.bmp`, `.gif`, `.heic`, `.jpeg`, `.jpg`, `.pdf`, `.png`, `.tiff`, and `.webp`.
 - **High Res**: For all other [supported file types](/ui/supported-file-types), and for the generation of bounding box coordinates.
-- **Fast**: For text-only documents.
+- **Fast**: For text-only documents.
+
+The **Auto** partitioning strategy routes each file as a complete unit to the appropriate partitioning strategy (**VLM**, **High Res**, or **Fast**) 
+based on the preceding file types. Additionally, for `.pdf` files, the **Auto** partitioning strategy routes these files' pages 
+on a page-by-page basis, as follows:
+
+- A page is routed to **Fast** when it contains only embedded text and no images or tables are detected.
+- All other kinds of pages are routed to **VLM** or **High Res**, depending on the complexity of a page's 
+  content. Unstructured constantly optimizes its proprietary algorithm for routing to **VLM** or **High Res** in these cases.