This seems related to a similar error when trying to Export pages that were named by another program. In my previous upload, try extracting the last two pages to their own file.

I also noticed that if I print to PDF from the PDF, the names of the new pages are their positions in the original PDF, instead of starting at 1 or keeping the original labels. See attached.

Also, if I print from PDF to PDF, it chops up some images and doesn't align the pieces quite right, but that's a separate issue.

Another workaround I tried was printing the two pages to PDF from Publisher, but it forgets some of the symbol fonts I use. I'm not sure who manages that engine, but that's that.

Currently, my only solution is to export the whole thing to multiple PDF files, then delete the pages that don't belong in each one by one in order to get separate downloadable files for each brochure. Tedious, but effective.

I see:
2020 Release (Classic) | Version 2020.004.30005
Version File Version: 20.004.30005.42714
I am also using Windows 10, 21H1 build 19043.1055

In this file, Organize pages, select the first 2-6 pages, click the trashcan icon on the toolbar. This is where I get the error

Hello Joseph,

Thanks for reporting the issue.

We are not able to reproduce this issue at our end on latest builds.
Can you please share the build number ??

Regards,
Gaurav

If the pages have labels instead of numbers and you select multiple pages to delete in Organize Pages, it gives the error "Please enter a valid page range." For me it does not matter whether it is consecutive or not, both give the same error. The only option for deleting is individually using the icon while hoving over the page.

I run into this problem most with files exported from MS Publisher and PowerPoint that have labels for the pages or slides.

It is a nuisance, but since I use these files frequently, I would appreciate a fix.