Home tab, the pilcrow icon. Page and section breaks become visible.
Put the cursor on the dotted line, press Delete, then recheck the page count.
Extract 1-4,6-20 to skip page 5 without editing the original.
A converter renders what the document says. A blank page in the PDF was a blank page in Word, and Word hides it well: a manual page break, a paragraph told to start on a new page, a section break set to odd page, or a table that ends exactly at the bottom margin and pushes its trailing paragraph mark onto a new page.
Turn on the pilcrow button and the invisible characters appear. A page break shows as a dotted line labelled Page Break; delete it and the page is gone. An empty paragraph carrying the page-break-before setting is harder to spot: put the cursor just above the blank page and look at the paragraph settings.
A table that fills the page leaves one paragraph mark after it. If that paragraph has 1.5 line spacing or a large font it does not fit, so it starts a new page containing nothing. Setting the trailing paragraph to 1pt with exact spacing removes the page without touching the table.
Delete the page from the PDF instead of rebuilding the Word file. Extracting every page except the blank one produces a clean document in seconds, and for something that is about to be sent, that is the whole job.
No. It reproduces them. They come from the source document layout settings.
Usually a trailing paragraph or table overflowing the bottom margin by a few points.
Yes. Extract the pages you want from the PDF, listing every page except the blank one.