File ▸ Export… saves the open note in the format you pick: Text, Markdown, HTML, HTML with Attachments, PDF, RTF, Open Docx, Open Odt, Text Bundle Markdown and Text Bundle Html. File ▸ Export Markdown… (Ctrl+E) goes straight to Markdown. Charts and formulas that were never shown on screen are drawn before the PDF and the HTML are written.
File ▸ Share… sends the note as Markdown, PDF, Text, HTML or RTF to another app through the Share panel of Windows. With several notes selected in the list, they are shared together.
File ▸ Page Setup… (Ctrl+Shift+P) chooses the paper; File ▸ Print… (Ctrl+P) prints the note.
File ▸ Open… (Ctrl+O) brings .paragraph, Markdown and text files in as new notes; so does a double-click on a .paragraph file in File Explorer. A .paragraph file opens the same on every device where Paragraph runs.
Your notes are folders inside %LOCALAPPDATA%\Paragraph. Edit ▸ Preferences… ▸ Advanced ▸ Reveal Data Folder in Explorer shows them.