Fun experiment alexwlchan! Two small mistakes in your post: you write "15,000,000,000.00 in" and "that the size of a page is 15 billion inches", but it should be 15 million.
You said you had difficulty formatting text. Here is a "hello world" pdf that just has these two words on a page: copy and paste this text (stripping leading spaces on each line) and save it in a .pdf file. Basically in order to write text you have to define a font (object 5) and then a stream with a Tf command to use the font, a Td command to position the text, and a Tj command to write it.
You said you had difficulty formatting text. Here is a "hello world" pdf that just has these two words on a page: copy and paste this text (stripping leading spaces on each line) and save it in a .pdf file. Basically in order to write text you have to define a font (object 5) and then a stream with a Tf command to use the font, a Td command to position the text, and a Tj command to write it.