Probably easier to export to PDF first, then remove the pages you don't want, or extract the pages you do to a new file, using Acrobat.
Would it not be easier to use the move pages feature in InDesign from one doc to another, only moving pages 41 to 51?
It may not be clear to you why Peter and 33 are advising some route to get to "PDF of pages 42 through 52" that doesn't involve deleting any pages. It's because we don't know how your document is built. It's not hard to delete pages 1 through 41, but if there's a threaded story that starts on page 20 and continues through page 50, then when you delete 1-41, the content from 20 will get pushed up to page 42. Maybe you've already experienced this. So it's hard to know exactly which method to recommend, but ones where you have to do separate deletions of content and of pages are not on the easy end of the spectrum, so no one is mentioning 'em.
One method even easier than deleting content & pages from an INDD, or pages from a PDF, or moving pages from one INDD doc to another is simply specifying what pages you want in your PDF at export: