New location of cache in Firefox 21

This was an annoying change for me and had to dig a bit to find it.

The location in Linux (Ubuntu) changed from:

There is also a seemingly new “thumbnails” that grabs a screenshot of each webpage we visit:

Shrink PDF file size in Linux

The problem:
I scanned a single document using Simple Scan, and it came out as a PNG (it defaults to JPG, but I changed to PNG to avoid pixelization).
I then converted at the command-line to PDF format (convert file.png file.pdf).

The resulting file was over 13MB, still too much for many email systems.

[Yes, I figured out since then that I could save it directly from Simple Scan to PDF simply by changing the extension. I still got a smaller file with the following method, which is also useful for PDFs that someone may give me.]

Someone suggested the following commands to shrink the file (from a terminal window):
pdf2ps file.pdf
ps2pdf file2.pdf

This worked really well, and reduced the PDF file size by more than 10x!