Today I learned that when a PDF's text includes URLs that are -not- marked up as hyperlinks, Adobe Acrobat Reader, Apple Preview, and Google Chrome's built-in PDF renderer all attempt to convert the URLs to clickable hyperlinks for the reader's convenience.

However, Adobe Acrobat Reader does a noticeably worse job than the other software. Specifically: if the URL is followed by punctuation, Acrobat includes the punctuation in the target of the hyperlink, resulting in a broken link. Apple Preview and Google Chrome handle punctuation correctly.

You can see this behavior by opening the attached PDF in Acrobat, Preview, Chrome, and Firefox. (The Microsoft Word document I used to produce the PDF is also attached). The PDF includes some hyperlinks, some plain text URLs, and a variety of punctuation.

The most interesting cases are #2 and #3:
- Adobe Acrobat converts both plain text URLs to hyperlinks automatically, but gets it wrong, including ALL the punctuation, including the comma, the quotation marks, and the closing bracket (if present).
- Apple Preview converts both plain text URLs to hyperlinks automatically, and gets it right, including no punctuation
- Google Chrome (for Mac) does NOT convert the URL in #2 to a hyperlink; it converts the URL in #3 correctly
- Firefox (for Mac) doesn't convert either of them.

If Acrobat were improved to behave like Apple Preview or Google Chrome, LOTS of documents around the world would start having working, clickable links for readers that use Acrobat. In particular, URLs in the footnotes/citations/bibliographies of a large number of scholarly publications would start working for people.