I don't know if synchronise the margins like the "Spacing to Contents" for frames etc. is very often useful.

Maybe the following will help you:
Format a document/template like you wish and save it. The easiest way to use it is to save it as a template in your template folder.

If you get a document open it in AOO and then use "Load Styles".

From the help:
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*Load Styles*
Imports formatting styles from another document or template into the current document.

|To access this command...
|Open Styles and Formatting window. Click the New Style from Selection icon and |keep the mouse button pressed. Choose Load Styles from the sub-menu.
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Select the document/template and select only [x]Pages to import the page templates.

Maybe you have to assign the wanted page style explicitly.

Created attachment 85475 [details]
Ways to Change Margins

Issue 126789 - Change all margins together in OO Writer


First Attempt:  Open Office Writer (two different methods)

Operating System:  Windows 7
Software:  Open Office Writer 4.1.2

Option 1 
  1) Open an OpenOffice Writer document:  
  2)  Choose “Format” from the tool bar 
  3)  Choose “Page” 
  4)  Choose “Page” again 
  5)  Set the four margins
Option 2 
  1)  Open an OpenOffice Writer document
  2)  Select “View” from the toolbar 
  3)  Select “Ruler” 
  4)  Adjust the ruler settings on the top and right-hand sides of the document

Findings:  Both of these replicate the actions that Malcolm experienced.  In both, you need to adjust the margins in four ways.  Option 1 is more precise than Option 2.   
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Second Attempt:  Microsoft Word (two different methods)

Operating System:  Windows 7
Microsoft Word Version:  2010

Option 1
  1)  Open a Microsoft Word Document
  2)  Select “Page Layout” from the toolbar 
  3)  Select “Margins” 
  4)  Set the four margins
Option 2
  1)  Open a Microsoft Word Document
  2)  Select “View” from the toolbar 
  3)  Select “Ruler”
  4)  Adjust the ruler settings on the top and right-hand sides of the document

Findings:  While not being a free software package, Microsoft Word is widely available.  However, just like in OpenOffice, you will need to adjust the margins in four ways.  Option 1 is still more precise than Option 2.
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Third Attempt:  Paint

Operating System:  Windows 7
Paint:  July 14, 2009

1)  Click on the “Start” icon on your computer 
2)  Select “All Programs”
3)  Select “Accessories”
4)  Select “Paint”
5)  Select “View” from the toolbar
6)  Select “Ruler”
7)  Select “Home” from the toolbar
8)  Select “Text” by clicking on the “A” 
9)  Place your curser on the 100-lenth, 100-width mark
10)  Copy and paste any text or write a document out inside the box
11)  Expand the box to the specified length and 1000-width
12)  Save the document and paste into a new OpenOffice Document and adjust the margins accordingly

Findings:  This method meets the criteria of free software; however, after going through 12 steps the best you’ll be able to come up with is a ½ page of content that will need to be adjusted on every ½ page of material.  So this misses the mark for longer documents and presents challenges for identical margin spacing for every pasted item.
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Fourth Attempt:  Snipping Tool

Operating System:  Windows 7
Snipping Tool:  February 9, 2012

1)  Open whatever document on which you need to change margins
2)  Click on the “Start” icon on your computer 
3)  Select “All Programs”
4)  Select “Accessories”
5)  Select “Snipping Tool”
6)  Select “New” and “Rectangle Snip”
7)  Keeping your margins in mind, draw around the information you want to be able to adjust
8)  Save the document and paste it into a new OpenOffice Document and adjust the margins accordingly

Findings:  This method also meets the criteria of free software; however, after going through 8 steps the best you’ll be able to come up with is a ½ page of content that will need to be adjusted on every ½ page of material.  So this also misses the mark for longer documents and presents challenges for identical margin spacing for every pasted item.

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Overall Observations:  Photographic capabilities are currently more challenging to use, as margin changing tools, than just going through the 4 – 5 steps necessary to change the margins in text documents.  I can only conclude that it is the reason this feature hasn't yet been developed.