Declaration of the National Anti-Slavery Convention was written by William Lloyd Garrison for the formation of the American Anti-Slavery Society in December 1833. It was reprinted in The Liberator on December 14, 1833. It is now available in the Public Domain.
You can also use the Optimized PDF option to crank the size down in very targeted ways. Given the big before/after shift, the culprit is probably the image you're embedding. Try exporting that file in various formats (PDF, jpg, png) and then import it.
Typically, it is best to have Acrobat Prompt you for a file name and location when. creating/saving the PDF. Adobe PDF Page Size. Acrobat is smart enough to recognize the page size of the original document and will convert it. to PDF using the same page size.