Alternatives to Adobe Acrobat and Adober Reader

On a mac, you will find 'Preview' superior for most purposes (reading & searching PDF's). Make sure you keep a backup copy of your original PDF (older versions of Preview killed the ability to save a fillable PDF). Preview has gotten better with each version. Now you can move pages by just dragging them from one PDF to the next.
Mac 'Preview'" To combine two separate PDF files into one document you need to drag the new pdf ON TOP OF an existing thumbnail until the double grey border appears -- then it will merge the two pdfs together. (You can then save the new merged pdf.) If you drag it into the sidebar but not on top of an existing page the new file will be added as an external link -- not merged into the original pdf document. See these two pictures below to visualise the difference

Merging & Splitting PDFs & Mac)
PDF Split and Merge is an easy to use tool to merge and split pdf documents. The GUI is written in Java Swing and it provides functions to select files and set options. It's made over the iText library.
PDFBinder is a simple tool that lets you merge any number of PDF documents into one, without having to resort to slow, user-unfriendly, expensive software.

Link to Using Adobe Acrobat to make a fillable PDF

It is not worth spending any more time on these instructions. Tell me of any errors so I can correct them. Feel free to ask me for help.