Deleting Text lines at top and Bottom of a page- Help for a PDF novice

I don't have the source files and I've got about 5 hours experience
using Acrobat Pro and some short term deadlines. So if you respond to
this post please be detailed I am a complete novice.

I would appreciate any help with the following problem. At the top of
each page of a pdf file there is one line of text in large red letters
and at the bottom of each page there is one line of different text in
large blue letters. The text doesn't seem to be part of the pdf file
but rather something that seems to be "overlaid" on to the pdf file.
I've listed what I've tried in the hopes that it will give someone a clue
as to what these lines are.

1). If I "edit->select", all the text at the top and bottom of each page
in the document is highlighted in blue. Nothing else in the document
is highlighted. But the the "edit->delete" is not active. So while
what I want to get rid of is highlighted there doesn't seem to be
anything I can do with it.

2). If I use "Tools->Advanced Editing->TouchUp Text", place the cursor at
the start of the line of text at the top of a page and left click the
mouse a blue box appears around the whole page. The line of text at the
top can then be highlighted by holding the left click on the mouse and
dragging the cursor across the line. Hitting the delete key then deletes
the line. The blue box then shrinks from bordering the whole page to just
line of text at the bottom. I can then repeat the above process and delete
this line.

3). If I use "Tools->Advanced Editing->TouchUp Object Tool", place the cursor at
the start of the line of text at the top of the page and left click the mouse
a blue box appears around the whole page. I can the hit the delete key and the
text at the top and bottom of the page is deleted for that page only.
Nothing else on the page is affected.

1) doesn't work. 2) works but has to be done a line at a time and for each page.
3) is the best of the lot but still has to be done for every page. There are a large
number of documents and most have hundreds of pages. Also the file size almost doubles
when I delete these lines from just a few pages of a document.

Adobe Acrobat Pro says that there aren't any headers/footers. The file properties show
that commenting is disabled. And I checked for layers and there weren't any.

My question is:

a). I'd like a method so that I can delete these lines for the whole document
with one command or do some kind of loop processing within a pdf file to
automate it.

b). Once I get these lines deleted, in some of thes files I'd like to replace
these lines with different text. How can I do this.

What are these lines? They don't seem to part of the original document but something that
was added after the fact. They seem to be objects of some sort.