I faced serious problems when it came to printing an OmniOutliner 3(pointsomething) document with multiple columns. Preview and print-to-pdf documents showed only (random?) enlarged details of the document, such as the column headers. Tinkering with the print optioons and/or app. preferences did not help. The solution that I found 16 desperate hours later: Export to Omni Outliner 2, re-import, and save the new document by overwriting the old one. This procedure apparently removes the bug – printing the document worked just fine!