In the spreadsheet app itself, you have the options to print only a specific sheet. You also can turn off the grid lines when creating the pdf from within the app. Is ther
Take a look at this code snippet: https://gist.github.com/4169590
What it does is uses Google Spreadsheet built-in download as PDF functionality so the same sort of customization is possible, including hiding gridlines and specifying a worksheet. Play with GET parameters to get the desirable output. In the end, script converts PDF file to a blob which you can manipulate further in your own script. To get this running though you'll need an additional authorization for Spreadsheet feeds scope.
Hope it helps.