A little addon to the htmlMarkup with table headers (THEAD) and table body (TBODY) tags will allow printing table head on each page (if printing large grids that are printed on different pages).
Concerning question printing large store, the grid prints the binded store. So make sure the store contains all data and you do not use filtering or paging (ex. paging plugin) or paging should be a very large value.
This solution should not be a genrall solution for printing very large data sets! In such a case you should generate print output on server side and maybe download it as PDF.
The plugin is thought as a quick and easy solution to print the visible grid part, including custom renderers, etc.
Currently all columns are printed, but it is also possible to filter hidden column, or prior print to hide some columns that contain html markup not needed to be printed in a later version.
var htmlMarkup = [
'<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">',
'<meta content="text/html; charset=UTF-8" http-equiv="Content-Type" />',
'<link href="' + this.stylesheetPath + '" rel="stylesheet" type="text/css" media="screen,print" />',
'<title>' + grid.title + '</title>',