A beta of Skim, a PDF viewing application, has been released. Skim is intended to make reading articles in PDF easier, and to permit marking them up with notes, bookmarks, and highlighting, just as you might with a paper copy. It has been created by the programmers and developers who created BibDesk, the bibliographic management program that integrates with BibTeX and LaTeX on the Mac. Recent nightly builds integrate with BibDesk, and my understanding is that more integration is planned. For instance, you could file a paper in BibDesk and annotate it without switching apps, or read a paper’s annotations in BibDesk.

Skim provides the ability to take a snapshot of a portion of a PDF; the snapshots can be stored in a dock or floated above the main viewing window. This is useful for keeping a particularly important figure or chart in view while reading past it. Extended tool tips show linked-to portions of text in a document: if an author has created internal links from in-text citations to references, you can see the reference without moving the main view to it by moving the mouse over the citation. A tool tip appears containing the reference. Notes and snapshots are organized neatly in a viewing pane. Full-screen and presentation modes are available as well.

I think it will be useful for teaching purposes: a professor might mark up and highlight a digitized copy of the week’s readings and distribute it to students on his or her course web page. This would be useful for something impenetrable, like, say Hegel or Wittgenstein’s Tractatus.

PDFLaTeX users might use it for collaborating, marking up and commenting on typeset PDF’s. Also, a PDFLaTeX user might use it for collaborating with non-TeXies, sending a PDF to be marked up and returned. It also might be used to comment on drafts of student papers, something I often do by inserting text into an RTF file provided by the student and emailing it back.

Skim is released under an open source license—it’s free, as in “freedom,” and also as in “free beer.” You can download it here.

I have used Skim regularly as my main PDF viewer for some weeks now, and I can attest to its stability and excellent user interface design. I highly recommend it. Together with BibDesk, it is one of the main reasons not to defect from the Mac OS to Linux or Open Darwin.

As with BibDesk, developers Christiaan Hofman and Adam Maxwell act quickly and decisively to feature requests and bug reports. You can sign up for the mailing lists here, and also find to the Sourceforge bug-tracker.

In a blog post, Mike McCracken, a chief developer of BibDesk and Skim, provides a more detailed account of Skim’s aims and functions, including screen shots of some of the more exciting capabilities it provides.