InDesign files can get clunky and slow, especially when you are building a portfolio. A useful tool to cut down on the lag and make the file easier to deal with, try using books instead.
Once you have your project samples created, check out the tutorial here, create a new book.
Go to the InDesign "File" drop down menu, and click "New", and then "Book".
You will see a box pop up that looks like an InDesign Library. Add the documents you have prepared in the order you want them and save the book.
Now if you click the settings, you will see a lot of options. This is where you can update your page numbering, reorder your documents, and much more.