Answer:
I know a word of letters three. Add two, and fewer there will be!
Never alive but practically extinct. How we miss the letters pressing the ribbon of ink. What is it?
I crawl on the earth. And rise on a pillar.
A mile from end to end, yet as close to as a friend. A precious commodity, freely given. Seen on the dead and on the living. Found on the rich, poor, short and tall, but shared among children most of all.
Salty water everywhere but not sea in sight.
Almost everyone needs it, asks for it, gives it. But almost nobody takes it.