Where can I find the data (e.g., xls files) for the xwalks referenced in chapter 4 of the user guide?

I would like to use the xwalks referenced in user guide. In the user guide there are links to pdf files, .e.g.,

https://usa.ipums.org/usa/resources/c…

https://usa.ipums.org/usa/resources/c…

https://usa.ipums.org/usa/resources/c…

etc.

Where is the underlying data?

I believe you are looking for excel spreadsheets for the occupation crosswalk codes. If so, they are available here.