I have scanned a document into a PDF at 300dpi. The document file is larger than I would like. Is there a simple way to down-sample the document so that it has a lower resolution? Or do I just need to re-scan the original document?
ImageMagick® is a software suite to create, edit, compose, or convert bitmap images. It can read and write images in a variety of formats (over 100) including DPX, EXR, GIF, JPEG, JPEG-2000, PDF, PhotoCD, PNG, Postscript, SVG, and TIFF.
For example, from a terminal:
convert input.pdf -resize 50% output.pdf
convert input.pdf -scale 50% output.pdf
Apple's Preview comes with a feature allowing you to save a file with a reduced file size.
Open your file in Preview, and click File>Save As.
Scroll down to the bottom where you will see a "Quartz Filter" drop-down menu and choose "Reduce File Size".
If you want to retain a copy of your original but larger file size, rename this file and click save. Otherwise you will overwrite the larger file when you click save.