The products are exactly the same it's just whether you are running them in Lite mode or Pro mode.
Both will search ANY text based formats, such as .txt files, or other forms of text files such as source code, e.g. .cs, .cpp, .h, .vb etc.
The encoding of the file (e.g. UTF-8, UTF-16) is detected based on the BOM at the start of the file. If no BOM Is found then the file is assumed to be ASCII (FileLocator Pro has some additional options for UTF-8 files).
The lite version of the product will search common Office formats (if the appropriate IFilters are installed), such as:
.doc, .docx, .ppt, .pptx, .odt, .ods, .sxw, .sxc, .xls, .xlsx
and also PDF files (but IFilters are not required for .pdf files).
The Pro version will search using ALL available IFilters on the computer, such as .wpd or .dwg, you can see the available list in the IFilter Settings.
The Pro version also includes specific 'interpreters' for these types:
.doc, .docm, .docx, .dot, .dotm, .epub, .odt, .ods, .ott, .pdf, .rtf, .xls, .xlsb, xlsm, .xlsx, .xltm
.msg, .pst, .ost, .eml, .mbox
.7z, .cab, .arj, .chm, .bz2, .deb, .cpio, .dmg, .gz, .gzip, .iso, .jar, .hfs, .lzh, .nsis, .msi, .rpm, .rar, .tar, .txz, .udf, .wim, .xar, .xz, .z, .zip
Images (meta data)
.bmp, .emf, .gif, .jpg, .png, .tif
Music files (meta data)
.3g2, .aif, .asf, .flac, .mp4, .m4a, .m4r, .m4b, .4mp, .mp3, .mpc, .opus, .ogg, .spx, .wav, .wma, .wv
If you have a file type which is simply an alias for another file type (e.g. .jar is the same as .zip) you can add the file type in the extension settings.
The Pro version also includes a Compressed documents reader that can be used to search any file format that is based on the compressed Zip format.
Finally, if there isn't a format listed that you know how to convert to text you can use the Custom Extension functionality to add additional formats.