Don't know if this is the right solution... but... this is how I did it:
1) Go to your admin area, login and click on the 'Structure' link in the main top menu/bar.
2) Click on the text link 'Content types'
3) Click on the 'Basic page (Machine name: page)' --> 'edit' link
4) Now click on the second Tab 'Manage fields'
5) Vertical under the column "Label" you'll see the text field 'Add new field', enter your desired name in this field... I've used the name "pdf documents"
6) Now under the column "Name" fill in a name
7) And under the column "Field" select in the dropdown the field 'File' and click on save
8) Now you will get a lot of option/selections... choice your own settings... I think you will need to make youre own settings here. I can't decide what you need/want here :)
9) Save everything when your finished, now create a new page/node or edit one and you will see right below where you normatively enter your page/node text... you'll see a upload field for the pdfs.
Good luck ;)