Edited PDF File Size

[Keith Hansen]

Interesting situation today... I took a very large PDF file (20MB). I
deleted all but two pages from the PDF and saved it. Yet, even though it
now contains only two pages, the file size is still shown as 20MB!

I then opened the PDF and saved it under a different name. It is now
only 140KB.

Why did the edited PDF retain the huge file size, even though it only
contained two pages? Why did the "Save As" bring about the file-size
reduction?

Just curious...

Keith