Merging PDFs on Windows

First you need Ghostscript.
Then, you can just issue the command:
> gswin32 -dNOPAUSE -sDEVICE=pdfwrite -sOUTPUTFILE=merged_file.pdf -dBATCH file_1.pdf file_2.pdf file_3.pdf

What I noticed is that the text in the merged file is a little bigger than the original one at the same magnification although nothing is missing.
Maybe you/we need to tweak a bit with the parameters...

Linux Toolbox: pdftk

(from the man page) If PDF is electronic paper, then pdftk is an electronic staple-remover, hole-punch, binder, secret-decoder-ring, and X-Ray-glasses. Pdftk is a simple tool for doing everyday things with PDF documents. Use it to:

• Merge PDF Documents
• Split PDF Pages into a New Document
• Rotate PDF Documents or Pages
• Decrypt Input as Necessary (Password Required)
• Encrypt Output as Desired
• Fill PDF Forms with X/FDF Data and/or Flatten Forms
• Generate FDF Data Stencil from PDF Forms
• Apply a Background Watermark or a Foreground Stamp
• Report PDF Metrics such as Metadata and Bookmarks
• Update PDF Metadata
• Attach Files to PDF Pages or the PDF Document
• Unpack PDF Attachments
• Burst a PDF Document into Single Pages
• Uncompress and Re-Compress Page Streams
• Repair Corrupted PDF (Where Possible)

Get it on Fedora:
> yum install pdftk

Note Unfortunately pdftk was removed from the Fedora repository due to a license issue that prevented it from being used in nuclear facilities. Yeah, right. Okay. Whatever!
You have to recompile it from the sources or... grab the final product from someone who already did it: Professor Kriehn's Fedora Repository!

Converting to PDF from Openoffice (Linux)

There are basically 2 options to convert an Openoffice doc into PDF:

1. Use File --> Export to PDF
2. Print to file using File --> Print, which gives you a Postscript version of the doc. Then use ps2pdf to convert to PDF.

Well, what I've seen is that method 2 gives a much better result graphically speaking (with method 1, you sometimes get mingled/not correctly spaced characters), and smaller files. So, I'd really suggest you use that for the task.

Converting to PDF Under Windoz

First you need to get your doc into Postscript (PS) format. One way is to print to file using any PS printer (I use the HP Color Laserjet 8550-PS). Of course you don’t need to have it!

Install Ghostscript and Ghostview.

Open a PS file with Ghostview to be able to make the initial configuration. Choose from the menu: File –> Convert.

Select:

Device: pdfwrite

Resolution: 720

Options: -dMaxSubsetPct=100 -dCompatibilityLevel=1.2 -dSubsetFonts=true -dEmbedAllFonts=true

You’re set!

Reference: Creating PDF Files in Unix and Windows