If you work with multicolumn PDF documents in Preview, here's a handy time-saver.
You're probably familiar with Preview's text-selection tool, accessed via either the Tools: Text Tool menu item or Command -2.
Using this tool, you can drag to select and copy a section of text from a PDF
(as long as it's not protected), and then paste that selection to the Clipboard.
But with multicolumn documents, this doesn't work as you might expect - when you drag the cursor down to capture one column, for instance, Preview
captures all the columns on the page.
This can be quite frustrating, and makes it difficult to get just the text you want out of Preview.
Luckily, there's a workaround.
After you make the text tool active, press and hold the option key. The cursor will change from the text I-beam to a small cross. While continuing to press the option key, drag a rectangular region around the desired text. This trick makes it a piece of cake to capture just the column you want.