Update PhantomJS_MultiPage.js

Math.max(document.documentElement["clientWidth"], document.body["scrollWidth"], document.documentElement["scrollWidth"], document.body["offsetWidth"], document.documentElement["offsetWidth"]);
Math.max(document.documentElement["clientHeight"], document.body["scrollHeight"], document.documentElement["scrollHeight"], document.body["offsetHeight"], document.documentElement["offsetHeight"]);
Did not reveal the actual page height. Page height may be affected by viewportsize
In order to determine the split ranges in this particular case, I set my viewportsize and created a full output of the page.
Then, I determine the pixel range of pages and amount of padding.
This does not currently split the total pixel height of the rendered page into single pages dynamically because I could not reliably get the rendered pixel height without rendering the image first.