# Why can't I change the Magnification in Printout Style in Default.nb

This happens with Mathermatica 10.3.1.0:

When working with a notebook, I can choose between different working environments. However, they inherit their settings from Default.nb situated at

c:\Program Files\Wolfram Research\Mathematica\10.3\SystemFiles\FrontEnd\StyleSheets\Default.nb

on my Windows7 computer. In Default.nb the local definition for all styles in environment printout has Magnification->0.72 which yields printouts with too small characters (compared to the line length). Therefore my printed notebooks are not reader-friendly.

Also I use some text cells with hanging indentation, e.g. ParagraphIndent->-80, TabSpacings->{4.4}. I begin those cells with a number or with a keyword, then a tab and then the rest of the text. Then the rest is indented by 80 printer points with respect to the beginning of the outdented keyword or number. The tab position is in those not well understood ems units. I just figured out that the combination of ParagraphIndent -80 and TabSpacings 4.4 looks good on the screen as long as I stay with Magnification->1.25, my favourite setting with the sreen I use. However, if I switch notebook magnification to something else, my carefully made indentation gets out of order (but it restores itself, as soon as I return to magnification 1).

If I print my notebook the carefully chosen indentation gets out of order on the printout. To my understanding this is due to the implicit change of magnification to environment printout.

Therefore I want to change the setting in

and I hit Shift-Ctl-E:

and want to change the setting from 0.72 to 1.0. However, I only can mark the entry, but I am unable to change it! If I type a number, it won't!

I try it using OptionInspector for the cell:

I can't change the number! This even happens, if I try to do all this on a copy of Default.nb in c:\temp, where I definitely have writing rights.

What's wrong?

in the top corner of the cell bracket you will see a strange pattern which actually means that the cell is not editable. You can confirm this by clicking on the cell bracket and then going to the options inspector and looking up editable. You should not edit the default or core stylesheets. Create your own stylesheets as per several examples here and modify the magnification on the Printout style.
CellPrint[Cell[StyleData[All,"Printout"],Magnification->1.0]] This should change the magnification to 1.0 (or whatever number you enter).