Leanify is a lossless file optimisation tool. Point it at a supported file and it removes unnecessary data, without affecting the core contents (images are reduced but quality remains the same, for instance).

The program can handle a range of formats: APK, Office 2007-2013 (DOCX, XLSX, PPTX), DWF/ DWFX, EPUB, FB2/ FB2.zip, GFT, GZ/ TGZ, ICO, JAR, JPEG, LUA/ LUAC, ODT/ ODS/ ODP/ ODG/ ODF, PE (EXE, DLL, SYS, OCX, SCR, CPL), PNG, RDB, SWF, SVG/ SVGZ, TAR, XML/ XSL/ XSLT, XPI, XPS/ OXPS, ZIP.

The individual optimisations are quite small - remove metadata here, try a recompression there - but they can add up. Especially as Leanify compresses the contents of a file, as well as the file itself (the JPEGs within a DOCX within a ZIP).

Leanify is a console-based tool, which makes it a little trickier to use. But only a little. Right now your command line options look like this:

Usage: Leanify [options] path1 path2 path3 ...
 -i <iteration> More iterations means slower but better result. Default: 15.
 -d <max depth> Maximum recursive depth.
 -f  Fast mode, no recompression.
 -q  Quiet mode, no output.
 -v  Verbose output.

Not too much to learn, and at a minimum you can just drag and drop a file onto Leanify.exe and watch as it's compressed.

Be very careful, though. Any files passed to Leanify are overwritten by default, and although the program does its best not to cause any harm, some optimisations may present problems. Always work with copies of files, never the originals, and test the optimised versions carefully to confirm they work as you expect.