I would recommend searching online for any software which can be used to create PDF documents. Anything that will do the job for you for free would be a good place to start.
ZIP files are an entirely different format that aren't directly related to PDF files. I would not worry about the ZIP format unless you had many different PDF documents that can't be combined and you wished to sell them all at once. Then you could package all of those files in a single ZIP file. But since you just have several pages that need to be combined into one PDF document a ZIP file won't be necessary.
