Sioyek beats SumatraPDF for academic text work. Sioyek has Overview[0], Smart Jump and more features that helps academic text studies. Digital versions of page earmarks, pen highlighting and margin notes that are common in academic text usage. It feels like the main developer and contributors have personal experience of that kind of use and gear the application for it.
In contrast the SumatraPDF dev seems focused mostly on light, casual PDF viewing. Read short pdf files from start to end, add a few highlights, occasionally search.
One good feature SumatraPDF used to have, but removed, was an option to store annotations (such as colored text highlighting) in external .smx sidecar files. Similar to how VLC and other video players support sidecar .srt subtitle files.
Since a few years SumatraPDF now only writes annotations into the PDF file. That has some advantages (greater cross reader annotation compatibility, all in one file) but also disadvantages:
- Third party tools can't search or operate on the plaintext annotations. With the sidecar approach if highlighted text were to be stored as plaintext with location data in the sidecar file third party tools could use ripgrep or similar to do fast, powerful searching and filtering on highlights across a whole pdf collection.
- Annotation versioning.
- No convenient way to load different sets of annotations for a single file. Useful for academic text work where one source document may be highlighted differently for different research topics. With an API and support for third party tools toggling such sets could be instant and very user friendly. Without sidecar files the user has to keep separate copies of the pdf file and write different annotations to each.
- Modifying the source pdf can be an issue where text integrity is crucial. Many pdf documents are used as a shared source of truth and simple hashing can verify that all parties use the same unmodified document. That gets more complicated when annotations are written into the file, since different pdf applications do such writing differently.
Even though Sioyek is better for academic work I think there is a lot more to do. In some ways academic text work on a physical book still has a better UX. For example a glance at the edge of a physical book gives an overview of the earmark locations. A digital version of that would be a code editor minimap style sidebar that overview highlight and bookmark locations in the whole pdf document. The minimap could have a heatmap feature that colors (and gradually fades) locations the user recently has viewed in the pdf. As a way to mitigate getting lost when jumping between locations in a digital document.
[0] https://github.com/ahrm/sioyek#overview