Remove background from pdf file

[life24]

Hello,
I can't remove background from this pdf file
I attached PDF file.

and pdf file is
http://docs.zarup.com/105847-download-Chapter_2.pdf.html

 

[corkyg]

Why not just copy the text and forget about the background?

 

[life24]

I think it's takes times.

 

[bruceb]

The information here may be able to do it.

http://solvengineer.com/blog/2015/01/how_to_quickly_remove_backgrou.html

 

[life24]

I try above method but don't get good result