This is an example of problems when using a proprietary filing system to save documents. As @ronguest suggested, using the Mac’s standard file system is perfectly adequate. These days, there is little advantage to using a proprietary app to store files long-term.
Back in my old Windows PC days, I used the app “Paperport” to store documents. Big mistake. This app initially stored documents in its proprietary format (.max files). In later years, Paperport supported .pdf files - but too late, as I had thousands of files in the .max format. Paperport was not available for OS-X (later macOS), probably because the Mac operating system supported .pdf files natively. I struggled for years trying to convert the old .max files to a usable format.
Lesson learned: Don’t use a proprietary app or file format for long-term storage of documents.