Usually, people use InDesign for portfolios, then they export as a PDF. I don't know what else to tell you. 

Well using InDesign is I think the fastest way, but you can also use Illustrator. You can put every page of your portfolio in a separate artwork organized in the same file and then save as pdf. The save-as settings also allow you to compress the files so it's smaller file size, but be careful of resolution.

Most of the time schools have just used slideroom, so this is new. Thank you!

Use InDesign to make portfolios, illustrator is for vector work (Images make the file size massive). Regardless, if you create individual files on PC you can highlight and select "combine supported files..." (they don't even have to be pdfs, image formats can be combined into a pdf.) or for any OS open acrobat and select combine files. This all hinges on having acrobat. If you don't you can use another pdf editor like foxit.  If you don't want to download a program there are websites where you can upload your pdf to combine it and then download it. If the file size is too massive save as optimized pdf.

^well if you link images into Illustrator it's not as big of an issue for size. That is inherently what ID is doing anyway, so in that sense they are similar.