The only way to combine two LiveCycle forms is in Acrobat. There is a button at the top in Arobat Pro that say "Create". Click that and select PDF Portfolio from the bottom of that list. You can then pick how you would like your portfolio to look and work, and then click the "Add Files" button. You can add as many files as you need to. The display can be customized by changing the color themes, importing a background image or map and creating a custom header. The nice thing about a portfolio is that it can contain a variety of files, not just LiveCycle forms. You can import Word files, videos, music, whatever and when the user selects a file, it will open the native program that they have installed on their computer to run it. Individual pages can be extracted and saved to the user's computer, forms can be filled in and saved back to the portfolio.
The portolio is then saved as a pdf and the total size is less than the sum of all of it's parts. It can then be emailed and opened by anyone with the free Adobe Reader. We use it to combine brochures and forms in the same pdf to make it easy for our clients to access everything they need.
Hope this helps.