# Guides

> Practical, first-hand guides on PDF conversion, compression, page sizes, OCR, Markdown and document privacy.

- Page: https://acepdfmd.com/guides/
- Runs at: https://acepdfmd.com (Uploaded files are deleted within 60 minutes. No signup for light use.)
- Also in 29 languages: https://acepdfmd.com/<lang>/guides/

- [Markdown Cheat Sheet: Syntax Reference with Examples](https://acepdfmd.com/guides/markdown-cheat-sheet/): This reference lists every common Markdown element with a plain, one-line explanation and a short, copyable fenced code example.
- [PDF Page Sizes and Dimensions: A4, Letter, Legal and More](https://acepdfmd.com/guides/pdf-page-sizes/): This guide lists standard PDF page sizes in millimeters, inches, pixels at two resolutions and PDF points, with notes on each.
- [How PDF Compression Works and Why Some Files Barely Shrink](https://acepdfmd.com/guides/pdf-compression-guide/): PDF compression mostly means re-encoding the images inside a file, so the result depends heavily on what the file contains.
- [PDF to Markdown: How It Works and How to Use It for AI](https://acepdfmd.com/guides/pdf-to-markdown-guide/): Converting a PDF to Markdown keeps document structure while producing a format that is far cheaper to feed into an AI tool than raw PDF text.
- [OCR for PDFs and Images: How to Get Accurate Text](https://acepdfmd.com/guides/ocr-guide/): Optical character recognition reads the shapes of letters in an image or a scanned page and turns them into real, selectable text.
- [Is It Safe to Upload a PDF Online? A Privacy Guide](https://acepdfmd.com/guides/privacy-guide/): Uploading a document to any web tool means trusting that tool with its contents, so it is worth knowing what actually happens to the file.
- [Open and Convert iWork Files (Pages, Numbers, Keynote) Without a Mac](https://acepdfmd.com/guides/iwork-guide/): This guide explains what .pages, .numbers and .key files are, how to open them on Windows, Android, Linux or the web, and which conversion to use for each job.
- [JSON Tools Guide: Convert Documents and Data to JSON and Back](https://acepdfmd.com/guides/json-guide/): This guide explains how the JSON tools read and write files, the document format that PDF to JSON and Word to JSON produce, and which tool to use for each job.