If it's not hidden and you want to think out loud I'd recommend using Pablo's dev.highlighter.com

If it should only be visible to certain a certain user or group of users...I don't know...do we have closed groups on nostr already? 😀 

 We have group messages and secrete messages.
But I cannot choose pdf to upload and send yet 

 I'm ashamed to admit that I haven't really used anything other than amethyst and iris
 

 Do you have telegram?