There are in fact multiple PDF files, one per month. You can get to them by using the ‘•••’ icon in the Journal window, then select ‘Reveal in Finder’.
At the moment, this location is fixed. We have some ideas about improving and expanding the functionality in the future, in particular specifying a path.
In the meantime, you can create an alias of this folder and place it somewhere else for quick access. If you want the folder to show in e.g. Dropbox, do not use an alias, but create a symbolic link to the folder using the Terminal. Let me know if you would be interested in more specific instructions…
It’s done at periodic intervals, based also on the modifications you make to your entries. Upon a change in an entry, a notification is sent to a journal service in the app. While the notifications are fast (few seconds), the new journal files are only generated every few minutes to avoid constant CPU usage while you edit. However, if you go into the journal, and check the content, it’s generated immediately if a change has been logged (the file on disk will be changed within some minutes).
I am not sure it would necessarily bring much to have that interval user-specified. Maybe what would be more useful is to have an ‘Update Now’ button to force a refresh of the files. What do you think?