The following is a list of programs that may be useful for debugging any trouble regarding the fonts, keyboard or the PDFs. Their usages are well documented in their respective man pages:
xlsfonts, lists the XLFDs of the all fonts available to X.
xfd, shows all the glyphs of a font when available to X.
xset, resets various X options like fontpath.
xev, detects and shows various mouse and keypress events.
xkbcomp, besides other operations, prints the current XKB configuration in a single file.
xpdf, a PDF viewer.
pdffonts, shows font list of a PDF file.
ps2pdf, PostScript to PDF converter.
A detailed description of XKB, www.charvolant.org/~doug/xkb/
A one stop mall for Unicode based Bangla on Linux, www.bengalinux.org
Fonts in XFree86, also supplied with the XFree86 documentation as README.fonts and normally found inside /usr/X11R6/lib/X11/doc/
Bangla Localisation HOWTO, a good starting point for using Unicode based Bangla.