Nearly as important as tags in a PDF, page order assists the screen reader in reading the content in the proper sequence. It’s not so much an issue with straightforward one column (and no sidebars) PDFs, but when PDFs contain multiple columns, text boxes and or sidebars, it is important that the page order be checked.
To check page order, either click the page order icon in the navigation bar:
Or, using the menu bar, go to View > Navigation Panels > Page Order:
In the page order panel you can drag page elements around so they make sense when reading. If you’ve checked “Show Page Content Order” in the Touch-Up Reading Order Panel:
The blocks of similar adjacent content will be numbered in your PDF and it corresponds to the numbers in the Page order panel for that page:
[Warning] Sometimes when you change the reading order content on your page will disappear. Occasionally, by moving the reading order back to its original position, you can fix this issue*, but to be on the safe side, always save your document before doing any re-ordering.
*If you are not able to move the order of a particular block of text, you may be able to move the surrounding blocks of text instead. So in the example above, if you needed to move the block labeled 2 to the bottom, you could move the blocks of text under it above it. This may not always work (save your document first) but usually it does. Sometimes to get a hidden block of text back, I move the block up or down — even have given it a little shake — and it has re-appeared. It has something to do with other, sometimes hidden, elements on the page.