How can I write in nth column of a file in awk?

Question

For example:

abc
xyz
123
546

input.txt:

asdad
asdad
adghf
dfytr

I wanted to add the above column in 2nd c

Answer 1

In awk:

awk 'NR==FNR {x[NR] = $0} NR != FNR {print x[FNR], $0}' col1_file col2_file

Though its probably better to use paste