Sorry if this was asked but I did not see it.
I am using an iMac with Mailspring.
I do not have the ability to share from Preview or Finder a PDF document to the Mailspring app. I have set it as the default mail reader and it is checked off in the Extensions part of System Preferences. I was switching from MS Outlook because I couldn’t do it either. I can only share using the Apple Mail app.
Thanks in advance.