Open your document in Adobe Acrobat X.
Click “Tools” and then click “Protection.”
Click “Encrypt with Password.”
Place a check mark beside “Restrict Editing and Printing of the Document.”
Enter a strong password in the box labeled “Change Permissions Password.”
A strong password includes numbers, special characters and/or a
mix of upper and lower case letters.
Choose “None” for the “Printing Allowed”
and “Changes Allowed” options.
Click to clear the box next to “Enable Copying of Text, Images and Other Content.”
Save the document to commit your changes.
Forgot to add, I’m not sure if it will stop a screen capture like Irfanview or the Snipping Tool in Windows from capturing what is on screen.