[SapnaVishwas]

Apache should be
2.2.16-6+squeeze12 and not older.

Do you use mod_jk at all??? It can be replaced by mod_proxy in apache 2.2
Do you think you have time to convert apache to apache-worker and mod_fcgid and php-cgi?

[SapnaVishwas]

It would help if we had a little of your code to see how the return is handled.

object myMostExcellentInteger = 5;
int myInteger = int.MinValue;

if (int.TryParse(myMostExcellentInteger.ToString(), out myInteger))
{
     // Run some excellent code
}

[SapnaVishwas]

Personally, I’d recommend plain C. Have you done research to see if there are any language that is more appropriate to what you are trying to do?

Can you write the code that you think will run the slowest in both Perl and C and benchmark them?

C++ is a super set of C.
You probably know more about Objective C than I do
C# actually has nothing to do with C – it is much more akin to Java.

[SapnaVishwas]

If you are just setting the source to point to the PDF, you are leaving the ultimate decision in the hands of the browser and user settings.

I would attempt to use PDF.js to render the PDF instead:

https://mozilla.github.io/pdf.js/

[SapnaVishwas]

I would stick with the traditional jQuery/jQueryUI maybe for the drag&drop list items.

AngularJs seems too much for what you need, and AngularJsis coming out anyway 🙂
If you want to go a bit fancier you could use ReactJS but only if you really want to spoil yourself with something new.