Preview page up/down by Keyboard Option+Up/Down

preview-key-down.scpt

tell application "System Events"
	set frontmostProcess to name of first process where it is frontmost
end tell

tell application "Preview" to activate

tell application "System Events"
	key code 125
end tell

tell application frontmostProcess to activate

preview-key-up.scpt

tell application "System Events"
	set frontmostProcess to name of first process where it is frontmost
end tell

tell application "Preview" to activate

tell application "System Events"
	key code 126
end tell

tell application frontmostProcess to activate

private.xml

<?xml version="1.0"?>
<root>
  <vkopenurldef>
    <name>KeyCode::VK_OPEN_URL_APPLESCRIPT.preview-key-up</name>
    <url type="shell">
      <![CDATA[ osascript ~/Dropbox/AppleScripts/preview-key-up.scpt ]]>
    </url>
  </vkopenurldef>

  <vkopenurldef>
    <name>KeyCode::VK_OPEN_URL_APPLESCRIPT.preview-key-down</name>
    <url type="shell">
      <![CDATA[ osascript ~/Dropbox/AppleScripts/preview-key-down.scpt ]]>
    </url>
  </vkopenurldef>
  
  <item>
    <name>Preview page up/down</name>
    <appendix></appendix>
    <device_only>
    </device_only>
    <identifier>private.script.preview.pageupdown</identifier>
    <autogen>
      __KeyToKey__
      KeyCode::CURSOR_UP, ModifierFlag::OPTION_L,
      KeyCode::VK_OPEN_URL_APPLESCRIPT.preview-key-up
    </autogen>
    <autogen>
      __KeyToKey__
      KeyCode::CURSOR_DOWN, ModifierFlag::OPTION_L,
      KeyCode::VK_OPEN_URL_APPLESCRIPT.preview-key-down
    </autogen>
  </item>
  
</root>