http://www.opensourcery.co.za/2010/02/08/paginating-documents-with-couchrest-and-will_paginate/

announcement.rb

class Announcement < CouchRest::ExtendedDocument
  property :announcer
  property :content
  property :recipients, :cast_as => 'Array', :default => []
  property :archived, :default => false, :type => :boolean
  timestamps!

  view_by :announcer_archive,
    :map => "function( doc ) {
      if( doc['couchrest-type'] == 'Announcement' && doc.archived ) {
        emit( [ doc.announcer, doc.created_at ], 1 );
      }
    }",
    :reduce => "function( keys, values, rereduce ) {
      if( rereduce ) {
        return sum( values );
      }
      else {
        return values.length;
      }
    }"

  class << self

    def by_admins( archived = false, options = {} )
      options[:page] ||= 1
      options[:per_page] ||= 25
      view_name = archived ? 'by_announcer_archive' : 'by_announcer'

      WillPaginate::Collection.create( options[:page], options[:per_page] ) do |pager|
        results = paginate(
          options.merge(
            :design_doc => 'Announcement', :view_name => view_name,
            :startkey => ['admin', {}], :endkey => ['admin'],
            :include_docs => true, :descending => true,
            :reduce => false
          )
        )

        pager.replace( results )

        total = view( view_name, :startkey => ['admin'], :endkey => ['admin', {}], :reduce => true, :group_level => 1 )['rows'].pop
        if total
          pager.total_entries = total['value']
        else
          pager.total_entries = 0
        end
      end
    end

  end
end

announcements_controller.rb

class AnnouncementsController < ApplicationController

  def index
    pagination_options = { :page => params[:page], :per_page => params[:per_page] }
    @announcements = Announcement.by_admins( params[:archived], pagination_options )
  end

end

index.html.haml

= will_paginate @announcements