I’m afraid this will never work perfectly, because it depends largely on what Pages does with the data, which we have no control over.
Agenda will put rich text, and plain text, on the clipboard, but Pages will read that off and restyle it for your document.
Things you can try are:
- In Pages, use Edit > Paste and Match Style instead of just Edit > Paste
- In Agenda, use Copy As > Markdown or Copy As > HTML to see if that helps at all
Agenda is not a rich text editor like Pages. In Pages you can control all of the fonts and text sizes etc. In Agenda, we use a fixed set of styles. The focus in a note taking app is on speed, rather than flexible styling. So the two will never mesh perfectly, but hopefully you can find a compromise where you are left with only a little cleanup.
Note that Agenda also has export options like Rich Text. Perhaps exporting a rich text document, and importing that into Pages, will work better.