A simple AppleScript to automatically (lossless) compress a PDF using PDFExpert Compress Feature.

pdf_compressor.scpt

# Copyright (C) 2019 Rafael Papallas
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program.  If not, see <http://www.gnu.org/licenses/>.

set filePath to "~/Desktop/some.pdf"
do shell script "open " & quoted form of filePath
delay 1.0
activate application "PDF Expert"
delay 1
tell application "System Events"
	tell process "PDF Expert"
		click menu item "Reduce File Size..." of menu 1 of menu bar item "File" of menu bar 1
		delay 1
		tell pop up button 1 of sheet 1 of window 1
			click
			tell menu 1
				click menu item "Lossless"
			end tell
		end tell
		
		-- Wait until the compression is done.
		repeat until button "Save" of sheet 1 of window 1 is enabled
		end repeat
		
		click button "Save" of sheet 1 of window 1
		key code 36
		
		-- Close the compressed file
		click menu item "Close Tab" of menu 1 of menu bar item "File" of menu bar 1
	end tell
end tell