Adjusting margins in Reader

Question

Hello all, and thank you for taking the time to read this.
I'm trying to print a PDF of a document which original I don't have.  The document already has a significant margin, and Reader is adding 25 Milimeters.
If I were to print it straight, I would select "Scale to printing area" from "Page scale", at the print menu.  The thing is I have to print it at two pages per sheet, and cannot select both because there's no "Print multiple pages AND scale to printing area", it's one or the other.  So what I want is to reduce the margin Reader adds to the document.
The problem is I cannot get the margin size to be editable, the boxes are greyed out.
So, I have two questions:
1st-  How can I edit these values?  Are they set in some .INI file?  Which one, and where can I find it?  Are they set in the registry?  Where?
2nd-  Why are these values shown if you can't edit them?  What's the point?  How can be possible that a company as important as Adobe can make such a mistake in a soft as important as Reader?  Why would they do that?  I just can't believe it.
Thank you all!

Answer 1

Hello.  Thank you very much for taking the time.
You can't change these values because they are irrelevant - they are not used for anything at all.
I believe they're.  In fact, it's 25 millimeters that are added to the page.  If you choose the "Fit to printing area" option, these spaces are removed (up to the printing area, of course).  But if you choose that option, you cannot choose the "Print multiple pages".  I might want (I do, in fact) to print multiple pages fitting them to the printing area.  It's funny they didn't think about that.
They are shown because this is a standard part of Windows, provided by Microsoft for all apps to use.
I don't think that's correct.  If you are a programmer, you know that when you create a form (like the one in the picture I took from this forum) it's you who decide which controls to include, not Microsoft or Apple.  If you put those text boxes and fill them with a value, you put them for a reason (nor Microsoft or Apple force you to) and most likely you relate them to a numeric variable that can be accessed (and changed) somehow from somewhere.
PDF files don't have a margin in the way a Word document does. They are more like a JPEG. There might be some white space at the edge of a page, where no words or pictures are. You see this as a margin.
I'm sorry, but it is a margin.  That's the concept of a margin: A white space between the contents of the page and the border of the sheet.
Adobe Photoshop also adds them when you print a picture, and you can manage the size of those... sorry: margins.
You can't adjust this white space (except, in Acrobat, by cropping it smaller - making the page smaller rather than the margin).
But then the margin stays the same, what changes is the white space inside the JPEG, to use your words.
(I know that doesn't solve the rest of it).
Nope, but thank you again for your answer. 
Even if greyed out, those values are not there just because.  They're set somewhere... in an INI file, in the Registry... I don't know... somewhere.  Windows doesn't make them up, even if it puts them there.  What I really need to know is where, but maybe it's not likely that a discussion like that would be allowed in this forum (companies don't like people messing around with the INI files or the Registry keys and values).  It's just I didn't find it anywhere else and though I had nothing to lose.