I recently faced the following problem: I had a PDF document created by merging several other documents, many of them containing multiple pages. I needed to display the page numbers in the document. Latex and pdftk to the rescue!

The Problem

I needed to generate a PDF by merging multiple unrelated documents from different sources, resulting in a 57-page file. After that, I had to display the page number in the header as “Folio x/57”, where “x” represented the current page number (“Folio is the Spanish legalese for “page”).

Manually adding the headers with the page numbers was too tedious, so I devised a two-step solution.

The Solution

The approach I came up with had two steps:

1. Generate a separate PDF with only the headers (“Folio x/57”) on each page.
2. Merge this with the original document, so that the headers are superimposed on top.

Generating a PDF with Only Page Numbers

I needed to create 57 mostly empty pages with “Folio x/57” in the top-right corner. The page number needed to update dynamically for each page. While this could be done in different ways, generating a PDF file was the most sensible options.

There were several tools to create such a document, but I choose Latex, because it offered the simplest and most customizable solution. Customization was crucial, particularly for adjusting margins, since the original document had inconsistent ones. The geometry and fancyhdr packages in Latex provided the flexibility I needed.

Here’s the code I used in pagination.tex:

\documentclass[12pt]{article}
\usepackage[paperwidth=8.5in,
  paperheight=11in,
  top=0.7in,
  right=0.5in,
  left=0.5in,
  bottom=0.5in]{geometry}
\usepackage{fancyhdr}
\usepackage{pgffor}
\pagestyle{fancy}
\fancyhf{}
\rhead{Folio \thepage/57}

\begin{document}
  \setcounter{page}{1}
    \foreach \n in {1,...,57} {
      \null\vfill\eject
    }
\end{document}

This script sets the document’s paper size and margins, defines the header format and then generates the pages using a loop, placing a new page break in each iteration.

If you are wondering why use \vfill\eject instead of \newpage, I recommend checking out this question in tex.stackexchange.com.

After compiling the LaTeX file, I obtained pagination.pdf, a beautifully blank document that displayed the page numbers in the appropriate places.

Merging the New Document with the Original PDF

The final step was merging the two PDFs –not just appending them, but actually overlaying them so that the headers from my new document appeared on top of the original content.

For this, I used pdftk, a fantastic tool for manipulating PDFs. The following one-liner did the trick:

pdftk original.pdf multistamp pagination.pdf output numbered.pdf

• original.pdf is the main document.
• pagination.pdf contains the headers.
• The multistamp option tells pdftk to overlay each page of pagination.pdf onto the corresponding page in original.pdf.
• The output flag generates the new, numbered PDF as numbered.pdf.

And that’s it! I managed to solve a tedious problem with just a few lines of code. Now I’m sharing them with you –and with future me 😉.