What is there about pdfs that needs a page. They are easy to make, just select it from MSWord or PowerPoint and make it .But it can be more than that.
There are many different kinds of pdf ifles. Each may have a very different kind of purpose. I have been creating and using pdf files since they began. A pdf file is basically a compressed file. Compressed files mean that some informaiton is removed and in one sense the different kinds of pdf files are choosing different kinds of information to remove while keeping the necessary information Where can you compromise on the quality of the file to make it smaller.
Sometimes you may have downloaded a pdf brochure from a software company and when you open it up to read it, there are screen captured samples of the software as it appears on the computer—And you cannot read it because its blurry even though you can read the words in the body copy perfectly. Or another time you download the pdf brochure and its 5 MB in size but you can read the screen capture perfectly.
There are many other considerations which can go into making the pdf file, some not so noticalble to the layman's eye, but are necessary for some other purpose, such as offset printing. Its not uncommon for different offset printers or journals to have different specs for pdf files (and they will tell you this in their specs for printing).
Basically one needs to make the right kind of pdf file for the purpose.