Hi Suvayu,

 > In this case, the corresponding lines in the org file and the exported
tex file would be helpful.

Please find two sets of files, one set named 'test' and the other set
'test1', attached herewith this email. In 'test' files, no preambles has
been used (only texts) and in 'test1' files few packages and other details
are there.

In the .org files, few lines have been underlined using underscore and the
files have been pdf exported.

If you feel that the problem is not related to org-mode, then ignore this
email and thanks for your time and patience.

-----------------------------
*Sanjib Sikder
*