Preview Cant Open Multiple PDF in same Window I have the option to open groups of files in same window setting turned on, and this works for pictures.

However, for PDFs this setting does not seem to work.

I know opening multiple PDFs in the same window was possible at least in Sierra, I have no idea if they changed anything for High Sierra that caused this to fail. 

I went through ~/Library/Containers/com.apple.preview/..../com.apple.Preview.plist
and found PVImageOpeningMode = 1

so this should be the correct setting, at least from what I know.

I tried getting my old ~/Library/Containers/com.apple.preview/fluff and replaced whatever setting I have right now ( it worked before ), and unfortunately I still cannot view multiple PDFs in the same window ( without using tabs ).

This is pretty vexing, right now im leaning on the conclusion that apple had some how changed how preview app works, unless there is another hidden preview setting location some where.

Has anybody found a solution to opening multiple PDFs in the same window in High Sierra?
You can open multiple PDFs in the same window, but the UI is different. Multiple PDFs will now open in separate tabs rather than the old way of segmenting them by scrolling.
Here is a link to the Apple support site if the following steps are not clear: https://support.apple.com/en-us/HT206998
To ensure all documents open in tabs follow these steps:
Big Sur
(Open) System Preferences &gt; (Select) General &gt; (Go down to 5th option) Prefer tabs: &gt; (Select from option menu^) Always
Older versions of macOS
(Open) System Preferences &gt; (Select) Dock &gt; (Go down to 5th option) Prefer open tabs when opening documents: &gt; (Select from option menu^) Always
Now, when you open multiple PDFs they will open within the same window, segmented by different tabs.
^From the option menu, you have the following options:

Always: When you open another window in your app, it automatically opens as a tab in your current window.
In Full Screen Only: When you open another window in your app, it opens as a tab only if you're using the app in full screen. Otherwise, it opens as a new window.
Manually: Manually choose when to use tabs, whether or not you're using the app in full screen.