MuPDF vs Skim

MuPDF is an embeddable SDK for developers working with PDFs and other document formats in desktop, cloud/server, or embedded projects. It supports viewing, editing, extracting, signing, rendering, redacting, annotating, splitting, merging, compressing, and converting documents. Listed inputs include PDF, ePUB, image formats, SVG, CBZ, and XPS; outputs include PDF, text, HTML, PostScript, print formats, PNG, SVG, and PNM/PAM. Developer bindings include MuPDF Core, PyMuPDF, MuPDF.js, and MuPDF.NET. The open-source release is AGPL-licensed, and embedding it in a product may require a commercial license. For server-based use of the open-source software, the licensing terms require disclosure of application source code to users interacting with it. Commercial licenses provide an alternative without AGPL code disclosure and include technical support and free upgrades. The Commercial plan is listed at $299 a month and includes one licensed domain and one preview domain for testing; a 14-day trial is also listed. Open-source users can seek community help through Discord and the bug tracker.

Skim has no write-up on Specifiction yet; its figures are above.