I was having a look at what apps I use the most this morning at work, and one of the apps I use the most (besides basic apps such as the browser and email client) is a little app called PDF Squeezer.
I deal with a lot of PDFs which need uploading and emailing around and this app has saved me so much time and energy. All you do is drag the PDF into it, change the compression amount (it remembers the last one you used so I hardly change this) and it outputs a nicely shrunk version. It seems to knock 30% off standard text documents and up to 75% off the school newsletters (they include lots of images).
It’s not the most exciting app but it is definitely a time saver and there is value in that! In case you are interested it can be found here.