[Tex/LaTex] How to place a 1 cm margin to a set pdf book (a6) to print

Question

So I've already got my book ready set for a6 paper: contents, latex compilation, and I'm already satisfied with the end result of pdf I've got. However I've noticed that it'd be good to add a small margin/offset binding to the left/inner side to have more space to glue/bind it all together.

Setting margins in the latex compilation would, even slightly, change the resulting pdf. I'm trying to avoid that step.
…Although one of the comments has already fixed that!! So a short answer/solution would be that comment suggested by touhami!

\addtolength\oddsidemargin{1cm} \addtolength\evensidemargin{-1cm}

The problem may be rather similar to insert pdf, add margin, or even a unpopular/unanswered question on margin width. This is one of the topics I've noticed most clogged with low qualified questions and answers. Is it possible to find a canonic solution?

I can't manage to give the margin on only one side from the done pdf. So the question is rather simple and even universal I hope:

Is it possible to place only a 1 cm margin on one side of a ready pdf?

(with an a6paper as end result)

Maybe a possible solution would most likely be similar to this post on what to do with a ready pdf to send it to print.

---

So I got answers and realized some important shit regarding margins offset/scaling.

If you get an offset margin in any size of paper, you'll get a scaled page, and you'll need to cut off the upper and lower margin so that the text doesn't get out of proportion.

• Nota bene. It seems it's best practice to go back to the book, before compilation, and set the outset there: this way it's possible to avoid using an exacto knife massively. …Also I'm sorry to admit that this whole question is a paradox. However, two answers dealed awesome with possible responses: Werner, on one hand, showed what the question was intending to do, and this brought the awareness of paradox. ph0t0nix, on the other hand, showed the new path that is needed, even if by surprise.

Answer 1

Let's create a bunch of random text:

\documentclass{article}
\usepackage[margin=15mm,paper=a6paper]{geometry}
\usepackage{lipsum}
\begin{document}
\sloppy\lipsum[1-50]
\end{document}

We'll call this work-of-art lipsum50.pdf. It consist of 25 pages of pure awesomeness, all of which is laid out on A6 paper with a 15mm margin. This should replicate your 130 page document.

Now we want to add an inner margin of (say) 1cm. That is, we need to place each page on the outside of pages that have an additional 1cm across the horizontal. The dimensions of A6 is 105mm x 148mm, so we'll set out paper size to be 115mm x 148mm.

We include lipsum50.pdf using pdfpages and set the offset=1cm 0pt within a "blank" twoside document:

\documentclass{article}

\usepackage{geometry,pdfpages}

\geometry{
  paperwidth=115mm,% A6 paper width + 1cm
  paperheight=148mm,% A6 paper height
  twoside
}

\pagestyle{empty}% Keep this document completely blank

\begin{document}

\includepdf[pages=-,offset=1cm 0pt,frame]{lipsum50}

\end{document}

I've added a frame to each page for visual clarity, but you don't need it.

If you want to maintain an A6 final output, you can scale each page down by a factor of 0.904762 (95mm / 105mm) and use an offset=5mm 0pt movement:

\documentclass{article}

\usepackage{geometry,pdfpages}

\geometry{
  paper=a6paper,
  twoside
}

\pagestyle{empty}% Keep this document completely blank

\begin{document}

% 95mm / 105mm ~ 0.9047619047619047619047619047619...
\includepdf[pages=-,offset=5mm 0pt,scale=0.904762,frame]{lipsum50}

\end{document}