You can export your notes to PDF or Markdown by right-clicking on the page and choosing Export, from the File menu, or you can export an entire notebook to one of the two formats.
If you export a page to a PDF and your images/equations are not showing up, try exporting it again.
Some flavors of Markdown support different features than others.
The exported markdown should be compatible everywhere except for Tables, KaTeX equations, and centered/right-aligned text/images. Tables are converted to the GitHub Markdown style and follow this structure:
The KaTeX inline equations are formatted as $equation$ and the block equations are formatted as:
Any text/images that has been right/center-aligned in your notes will be wrapped with
<p align='center'>text<p> which might not work on sites other than GitHub.
Images that have their data encoded directly in the document (such as screenshots that you paste in) will not be included in the Markdown file. It has to have a URL source.
So you may have to edit the Markdown file after exporting to make it follow the Markdown format of whatever website/software you're using it in.