Customizing the Index Page 
Filtering and listing resources is one of the most important tasks for administering a web application. Active Admin provides many different tools for you to build a compelling interface into your data for the admin staff.
Built in, Active Admin has the following index renderers:
- Table: A table drawn with each row being a resource (View Table Docs)
- Grid: A set of rows and columns each cell being a resource (View Grid Docs)
- Blocks: A set of rows (not tabular) each row being a resource (View Blocks Docs)
- Blog: A title and body content, similar to a blog index (View Blog Docs)
All index pages also support scopes, filters, pagination, action items, and sidebar sections.
Multiple Index Pages 
Sometime you may want more than one index page for a resource to represent different views to the user. If multiple index pages exist, Active Admin will automatically build links at the top of the default index page. Including multiple views is simple and requires creating multiple index components in your resource.
index do
  id_column
  column :image_title
  actions
end
index as: :grid do |product|
  link_to image_tag(product.image_path), admin_product_path(product)
endThe first index component will be the default index page unless you indicate otherwise by setting :default to true.
index do
  column :image_title
  actions
end
index as: :grid, default: true do |product|
  link_to image_tag(product.image_path), admin_product_path(product)
endCustom Index 
Active Admin does not limit the index page to be a table, block, blog or grid. If you've created your own custom index page it can be included by setting :as to the class of the index component you created.
index as: ActiveAdmin::Views::IndexAsMyIdea do
  column :image_title
  actions
endIndex Filters 
By default the index screen includes a "Filters" sidebar on the right hand side with a filter for each attribute of the registered model. You can customize the filters that are displayed as well as the type of widgets they use.
To display a filter for an attribute, use the filter method
ActiveAdmin.register Post do
  filter :title
endOut of the box, Active Admin supports the following filter types:
- :string - A drop down for selecting "Contains", "Equals", "Starts with", "Ends with" and an input for a value.
- :date_range - A start and end date field with calendar inputs
- :numeric - A drop down for selecting "Equal To", "Greater Than" or "Less Than" and an input for a value.
- :select - A drop down which filters based on a selected item in a collection or all.
- :check_boxes - A list of check boxes users can turn on and off to filter
By default, Active Admin will pick the most relevant filter based on the attribute type. You can force the type by passing the :as option.
filter :author, as: :check_boxesThe :check_boxes and :select types accept options for the collection. By default it attempts to create a collection based on an association. But you can pass in the collection as a proc to be called at render time.
filter :author, as: :check_boxes, collection: proc { Author.all }To override options for string or numeric filter pass filters option.
  filter :title, filters: [:start, :end]Also, if you don't need the select with the options 'cont', 'eq', 'start' or 'end' just add the option to the filter name with an underscore.
For example:
filter :name_eq
# or
filter :name_contYou can change the filter label by passing a label option:
filter :author, label: 'Something else'By default, Active Admin will try to use ActiveModel I18n to determine the label.
You can also filter on more than one attribute of a model using the Ransack search predicate syntax. If using a custom search method, you will also need to specify the field type using :as and the label.
filter :first_name_or_last_name_cont, as: :string, label: "Name"Filters can also be disabled for a resource, a namespace or the entire application.
To disable for a specific resource:
ActiveAdmin.register Post do
  config.filters = false
endTo disable for a namespace, in the initializer:
ActiveAdmin.setup do |config|
  config.namespace :my_namespace do |my_namespace|
    my_namespace.filters = false
  end
endOr to disable for the entire application:
ActiveAdmin.setup do |config|
  config.filters = false
endYou can also add a filter and still preserve the default filters:
preserve_default_filters!
filter :authorOr you can also remove a filter and still preserve the default filters:
preserve_default_filters!
remove_filter :idAllow Filtering Attributes 
By default, filtering on any model attributes is denied, this is a security feature to prevent users from filtering (reading by guessing) attributes that shouldn't be accessible by them. To allow filtering on attributes, follow the Ransack Authorization guide to extend ransackable_attributes class method.
Index Scopes 
You can define custom scopes for your index page. This will add a tab bar above the index table to quickly filter your collection on pre-defined scopes. There are a number of ways to define your scopes:
scope :all, default: true
# assumes the model has a scope called ':active'
scope :active
# renames model scope ':leaves' to ':subcategories'
scope "Subcategories", :leaves
# Dynamic scope name
scope ->{ Date.today.strftime '%A' }, :published_today
# custom scope not defined on the model
scope("Inactive") { |scope| scope.where(active: false) }
# conditionally show a custom controller scope
scope "Published", if: -> { current_admin_user.can? :manage, Posts } do |posts|
  posts.published
endScopes can be labelled with a translation, e.g. active_admin.scopes.scope_method.
Scopes groups 
You can assign group names to scopes to keep related scopes together and separate them from the rest.
# a scope in the default group
scope :all
# two scopes used to filter by status
scope :active, group: :status
scope :inactive, group: :status
# two scopes used to filter by date
scope :today, group: :date
scope :tomorrow, group: :dateIndex default sort order 
You can define the default sort order for index pages:
ActiveAdmin.register Post do
  config.sort_order = 'name_asc'
endIndex pagination 
You can set the number of records per page as default:
ActiveAdmin.setup do |config|
  config.default_per_page = 30
endYou can set the number of records per page per resources:
ActiveAdmin.register Post do
  config.per_page = 10
endOr allow users to choose themselves using dropdown with values
ActiveAdmin.register Post do
  config.per_page = [10, 50, 100]
endYou can change it per request / action too:
controller do
  before_action only: :index do
    @per_page = 100
  end
endYou can also disable pagination:
ActiveAdmin.register Post do
  config.paginate = false
endIf you have a very large database, you might want to disable SELECT COUNT(*) queries caused by the pagination info at the bottom of the page:
ActiveAdmin.register Post do
  index pagination_total: false do
    # ...
  end
endCustomizing Download Links 
You can easily remove or customize the download links you want displayed:
# Per resource:
ActiveAdmin.register Post do
  index download_links: false
  index download_links: [:pdf]
  index download_links: proc{ current_user.can_view_download_links? }
end
# For the entire application:
ActiveAdmin.setup do |config|
  config.download_links = false
  config.download_links = [:csv, :xml, :json, :pdf]
  config.download_links = proc { current_user.can_view_download_links? }
endNote: you have to actually implement PDF rendering for your action, ActiveAdmin does not provide this feature. This setting just allows you to specify formats that you want to show up under the index collection.
You'll need to use a PDF rendering library like PDFKit or WickedPDF to get the PDF generation you want.