create a publication that has both portrait and landscape pages

[Ed]

how do I create a publication who's primary layout is in Portrait, but
requires a landscape layout occasionally?

 

[Ed Bennett]

how do I create a publication who's primary layout is in Portrait, but
requires a landscape layout occasionally?

You cannot. You could group and rotate all objects on such pages through
90°, or you could create two separate publications.

 

[Mary Sauer]

Select all on the page, rotate 90 degrees.