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.
PDFs use the following compression algorithms to reduce file size: 1  LZW (Lempel-Ziv-Welch, see Minimize Bit Depth) and FLATE (ZIP, in PDF 1.2) for lossless compression of text and images. 2  JPEG and JPEG2000 (PDF version 1.5) for lossy (or lossless for JPEG2000) compression of color and gray scale images.