Avast anti-virus incorrectly detects ACFPDFUI.DLL as a "virus" and deletes it. This is called a false positive.
To install Charting Companion on a system protected by Avast, you need to temporarily suspend Avast.
Click on the Avast icon in the System Tray (bottom right) to open up the Avast control panel.
 Active Protection
 File System Shield
 Turn off for 10 min or 1 hr. (button at right)
 Install Charting Companion
 Click on General, Exclusions, Path, browse to:
C:\Program Files (x86)\Charting Companion
 Turn back on Avast File System Shield