All users should be able to follow the reading order of your webpage, and this extends to those navigating using only a keyboard. Most users will expect the content to read from left to right, top to bottom, so creating proper order within the source code will allow the page’s visual order to be read as intended by assistive devices.
View WC3 information on creating a logical tab order.
Reading order also applies to your PDF documents. That means that, yes, you even need to pay attention to your document structure when creating PDFs that will be shared digitally.
To view the read order of your PDF in Adobe Acrobat Pro, go to View > Tools > Accessibility and select “Touch Up Reading Order.” Acrobat will show the order in which blocks of content will be accessed if navigating through the document with the keyboard. You are able to adjust items that are out of sequence in this view.
The “Touch Up Reading Order” view will typically give enough information to determine a document’s read order and accessibility, but if you need a more accurate measure of screen reader order, go to View > Show/Hide > Navigation Pane > Tags. You are able to adjust items that are out of sequence in this view as well.