[Lowerbounds, Upperbounds]

Sometimes I am given a PDF and I wish I could change its margins. For example, when I print out a conference version of a paper to study in detail, usually there isn’t much space on the sides to write my own ideas. I heard Fermat had a solution for this type of issue :P, but in the modern days, I use sticky notes. The same situation surprisingly arises even if you use PDF annotating softwares. Free or not free (no link for them), they simply do not support the “enlarge canvas” feature yet. All you can do is to insert electronic sticky notes. So much for the metaphor!

Now there is actually a technology called “reflowable PDFs”, which are PDFs that contain enough information to support reflowing its content to fit any width. You can see this page for a screenshot of a reflowed document. Reflowing works wonder for text-dominant documents like novels, but the PDF has to be specially prepared for reflowing to really work well. (Try View->Zoom->Reflow in Adobe Reader 8.)

But if the given PDF is not reflowable, we can still use some graphics editor and edit the PDF interactively. After all, a PDF is mostly a vector graphics file, modulo some potential embedded bitmaps, and so you can edit it like any vector graphics file. I’ve seen it done in Illustrator, and I guess some of the free software competitors like Inkscape or Scribus can do this kind of editing too. But using a command line tool would be far easier.

For a long while, I actually know how to change the margins of a PDF. (Turns out lawyers have essentially the same problem.) The trick is to use the pdfpages package with pdfLaTeX. You may recall that this package allows us to include specific pages of a PDF into our own document. Magically, it has a scale option (that is really inherited from graphicx)… This gives us the first batch file: pdf-rescale.bat. Execute

pdf-rescale.bat foo.pdf 0.8

and you will get foo-0.8.pdf, which is foo.pdf shrunk to 80%. I’ve found that 80% is a good default and so the third argument is actually optional. You can also specify a scale of larger than 1 for some journal articles formatted for smaller paper sizes. I can also imagine fancier applications in which you combine this idea with the geometry package (see this post) to control of the final outcome.

But since we are not changing the actual size of the paper, shrinking the content for a larger margin actually means, well, shrunk content. Conference proceedings are already typeset in a small enough font. Since the proceedings are in two columns, I had the idea to print each column on its own page. That will definitely give us ample space. After a lot of different attempts since last year, I finally managed to get the second batch file: pdf-1c.bat. Execute

pdf-1c.bat foo.pdf

and you will get foo-1c.pdf, which is foo.pdf but with one column per page. No kidding.

The following PNG illustrates these scripts using the title page of an old paper. The upper-left shows the original, and the upper-right is after shrinking to 80%. The lower-left and lower-right are the two pages from the one-column version. I have also attached the source PDF from which I generated the PNG. The key feature is that this PDF retains the text of the original—try search for the word “degree” and you will see. (At one point my solution was to assemble a bunch of PNGs representing each single column into a huge PDF. Although you can annotate on it electronically, you cannot search in it. It also prints slowly.)

Finally, I also note that it is in fact possible to prepare reflowable PDFs using pdfLaTeX or dvipdfm (there seems to be trouble if going through a PS), but I will save it for a later story. For now, you can experience reflowing a LaTeX PDF with this PracTeX article, which is actually on the use of the pdfpages package. Having played with reflowing for a while, I would say that the real deal-breaker for reflowable PDFs lies in the mathematical expressions. You can see this TUGboat article for some excellent macros on fine-tuning mathematical expressions. Now, try to reflow it…

P.S. If you write the corresponding bash scripts, please send them to me so that I can, with full acknowledgement, post them here. The only reason why I stick to batch files is to avoid extra dependencies.

Change PDF Margin Scripts: pdf-rescale.bat pdf-1c.bat

Update: Joshua Dunfield has ported the rescaling script to Linux. See the comments.