It happens more often these days. You get some form sent to you as a PDF. You print it out, and fill it in, and then you want to scan it back in and send it back. For one reason or another, my scanner likes to scan documents to JPEG files: one file per scan. Grr... 

In the past, I've used some PDF printer driver or other to solve this problem, but under the water they pretty much all use ghostscript, so why not do it directly. I used to install cygwin on my Windows machines to get access to utilities like this, but these days, Windows embeds a pretty much functional Ubuntu. 

So yeah - just directly using ghostscript. How hard can it be? Well it turns out that a bit of Googling leads you to typing some pretty gnarly command lines, especially since I had scanned a 15 page document into 15 separate JPG files. And then Adobe Acrobat didn't understand the resulting document. No good at all. So then I googled further and found this. 

It turns out that by installing not only ghostscript but imagemagick, the imagemagick "convert" utility knows how to do exactly what you want, presumably by enlisting the help of ghostscript. So simply by cd'ing to the directory where I had my scans, this...

$ convert *.JPG outputfile.pdf

... did the trick. Pretty neat, huh? Note to self.... 

I had scanned in a document with the intention of emailing it. (For this I usually use PDFCreator which allows you to aggregate the results of several scans into a single PDF.) On this occasion, I had scanned all four pages of the document before realising that with, my current scanner settings, the resulting document would be about 12MB. So I was faced with the choice of either scanning them all again, or finding a way to reduce the size of the PDF. A quick Google turned up this link, which gave the following command line to use with Ghostscript:

gswin32c -sDEVICE=pdfwrite -dNOPAUSE -dBATCH 
-dPDFSETTINGS=/ebook -sOutputFile=C:newFile.pdf C:originalFile.pdf


The reason I had Googled for a Ghostscript solution was that I already knew I had it installed as part of Cygwin. (I always install Cygwin on any Windows machine I need to use regularly - mostly for the SSH client, but I usually do a full install just so that all those useful utilities are just there. After a bit of poking, I realised that instead of typing "gswin32c" I just needed "gs". The rest of the command worked just fine, and I ended up with a PDF of somewhat less than 2MB.

So here's a hat tip to the Ghostscript contributers over the years. Thanks. Isn't free software great?