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.
How to Change PDF File Sizes. There are many compressors that one can use to change and indeed reduce the PDF file sizes. These compressors have been designed and created to enable ease of operation in changing PDF file sizes. There are quite a few applications where one can re-size the PDF file by simple select, drag and drop operations that are so very easy to perform.