General ⇒ How do I insert hidden text to pdf documents using LaTeX?

[kornaros]

I have some old dictionaries (in pdf format) that they are simlply scanned photos of the dictinary's pages. My question is:
Is it possible to insert some text information that one could search (using Ctrl F)? For example I would like to insert in the folowing pdf file http://www.mediafire.com/view/d4w8iuis8xvwu6a/522.pdf

some "hidden" text like 1)
the Greek words "Μομούθ", "Μομπόζ", "Μονφελκόνη" etc. which are simply the heading words found in this page.

2)or maybe the whole output text file from an ocr program that I manually corrected.
One could not see directly the text behind the image but could search it( to find the corresponding page/pages.)

A similar question: could I insert some visible information like page numbers, word headings etc (at some place on the top or the bottom of the page layout )that could read and print with the pages?