Do you want the window to pop out to maxium possible size?
Adjust Window [Resize to Fit] or Adjust Window [Maximize] can be used to do that.
Such a script is often specified in File Options (found in the File menu) to run automatically when the file is opened.
Margin size (for printing) is a different issue and has to be handled differently. The margin location is determined by the printer setup's currently selected options for page size and orientation combined with any margin settings specified in Layout Setup... for a given layout. You can see where the margin and page breaks are for a given layout by entering layout mode and checking for the heavy vertical and horizontal dashed lines. Keep in mind that just changing settings in printer setup can move these lines to different locations.
In the layout that I'm in there are the horizontal and vertical dashes. I want the page in browse mode to fit to this size... The issue is with different monitor sizes with in our company I want all the information to fit in to there screen size. At this time the can scroll up and over on the page showing the white.
Those dashes only show you the limits of what will or won't print given the page size and orientation currently selected in Printer Setup. It has no bearing on what will be displayed on your monitor.
Adjusting displays to different monitors can be a challenge. The starter solution I looked at did not make any adjustments to fit the monitor except to resize the window. What starter solution(s) are you using where you see this "automatic adjustment"?
There are ways to "anchor" objects in your layout so that they "stretch" when you expand the window. You may be able to design your layouts for the smallest monitor option and then anchor fields, tab controls and portals to get them to stretch out to larger sizes when viewed on a larger monitor.
Look up "Setting auto-resize options for layout objects" in FileMaker help for a more detailed description of this approach than I have time to type here.
Asset Management. When you r in layout mode you can see the line where the information stays with in. When you go back to browse mode it stretches to that line and you cant scroll over to the white side anymore.....
As long as there are no layout objects off the right hand side of your screen, you won't be able to scroll any further to the right. If you can scroll to the right into "white space" while in browse mode, some layout object has been located off to the right of the edge of your window. Example, If I edit the Asset Management layout to add the text "AAA" to the right of the dashed line, I now can scroll further to the right than I could before I added this layout text. Keep in mind that some layout objects can be invisible to you while you are in browse mode.
See the help section I've mentioned previously. This layout in asset management is using the "anchors" as described in that help article to "Stretch" or "slide" items near the top of the layout out to the right hand edge of your window.
It's more or less coincidence that the dashed line is aligned with the edge of the objects in your layout. If you change page orientation to landscape in printer setup, you'll see this line move to the right, but it will have no bearing on what you can or can't see or scroll to while in browse mode.