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.
Steps: 1  Open the PDF file to redact in Preview. 2  Black out text using any method you want (e.g. use the rectangle annotation tool with black as the color and choose the thickest border. 3  File > Save As, and choose an image format such as PNG or GIF.  Open the saved image file, then File > Save As, and choose PDF.