This can be done with pdflatex easily. You can e.g. use graphicx or pdfpages to import the pdf and a picture-environment to overlay it with some text. Here e.g. an example with eso-pic.
\documentclass{article}
\usepackage{eso-pic}
\usepackage{graphicx}
\AddToShipoutPictureBG*{%
\AtPageLowerLeft{\includegraphics[page=1]{test}}
\AtPageLowerLeft{%
\put(\LenToUnit{8cm},\LenToUnit{10cm}){\Huge\bfseries TEXT}}}%
\begin{document}
\mbox{} % to create a page
\end{document}
Based on an informal discussion entitled "how to update .aux file in LyX?" (with the current "stable branch maintainer", Jürgen Spitzmüller) it seems that LyX automatically reruns a file based on an evaluation of the .log file. Another motivation for this stems from the LyX documentation on Customizations (under the menu item Help > Customizations, section 5 Installing New Document Classes, Layouts, and Templates):
First, let us a say a few words about how one ought to think about the
relation between LyX and LaTeX. The thing to understand is that, in a
certain sense, LyX doesn't know anything about LaTeX. Indeed, from
LyX's point of view, LaTeX is just one of several “backend formats” in
which it is capable of producing output. Other such formats are
DocBook, plaintext, and XHTML. LaTeX is, of course, a particularly
important format, but very little of the information LyX has about
LaTeX is actually contained in the program itself.
For example, the default LaTeX warning message
LaTeX Warning: Label(s) may have changed. Rerun to get cross-references right.
would initiate a re-compile, while the etaremune-specific warning message
LaTeX Warning: Etaremune labels have changed.
Rerun to get them right.
was "a specific syntax" that needed to be considered. Another example from the totcount package:
Package totcount Warning: Rerun to get correct total counts on input line ???.
that is not referenced as a "LaTeX warning", but rather a "package warning". Moreover, there seems to be no interest in implementing a forced, full, recompile (more than once) option in LyX. So, if the change does not initiate "a known warning", no recompile will be performed.
A suggestion would be to post this, in the form of a full example of your document usage/structure that shows the validity of such an option as being a feature, on the LyX mailing list. See their Get involved or Mailing Lists page for a reference.
Best Answer
You can use Insert -> File -> External Material, which wraps the
pdfpagespackage. Documentation for pdfpages is available here.Another way which might be more appropriate is to insert the
.pdffile as if it were any other graphic (Insert -> Graphics...) and use thepage=noption. These options are passed to the\includegraphicscommand, which is part of thegraphicxpackage (which is documented here). A screen shot follows:Here are some screenshots of the
pdfpagesmethod: