Since 2001, Global Systems Science (GSS) books have been designed for easy reading both on paper and on computer display. Starting in 2010, all the books were converted, chapter by chapter, to web pages. To facilitate printing books on paper, there are "print-friendly" versions.
Between 2005 and 2010, the books were distributed only as PDF files. Those and the paper/PDF versions of 2001-2005, used some simple principles of page design that we call "Combined Online and Hardcopy Design" (COHD).
The trick is to realize that a person viewing the document on a computer will likely take advantage of a magnification feature to display only 1/2 page at a time (150% or so), making print size "larger-than-life" and very easy to read. However, in that mode, 2-column formats can be very cumbersome in that the reader has to alternately scroll up and down to go from column to column—very irritating.
If you use text-block/graphic arrangements shown on this page as "Desirable Layouts", the reader will never have to scroll up to read from the bottom of the first column to the top of the second column. They can keep scrolling down continually. On the contrary, "Undesirable Layouts" are "forbidden" since they force the reader into the undesirable up/down scrolling when reading from column to column.
Some of the arrangements shown have combination 1-column and 2-column layouts. In the 1-column text blocks, it's best to keep the column width under 5", since it's much harder to read very long lines of text. Other arrangements are possible: you can have 3 columns (appropriate for even smaller font sizes in hard copy). Just apply similar principle (imagine reader viewing only 1/2 page at a time—top/bottom) and it will be just fine. Each half page can be a readable "page unit" unto itself.