<apex:page controller="PagingController">  
  <apex:form >
    <apex:pageBlock title="Paging through Categories of Stuff">

      <apex:pageBlockButtons location="top">
        <apex:commandButton action="{!process}" value="Process Selected"/>
        <apex:commandButton action="{!cancel}" value="Cancel"/>
      </apex:pageBlockButtons>
      <apex:pageMessages />

      <apex:pageBlockSection title="Category Results -  Page #{!pageNumber}" columns="1">
        <apex:pageBlockTable value="{!categories}" var="c">
          <apex:column value="{!c.Id}" headerValue="Id"/>
          <apex:column value="{!c.Name}" headerValue="Name"/>
        </apex:pageBlockTable>
      </apex:pageBlockSection>
    </apex:pageBlock>

    <apex:panelGrid columns="4">
    <apex:commandLink action="{!first}">First</apex:commandlink>
    <apex:commandLink action="{!previous}" rendered="{!hasPrevious}">Previous</apex:commandlink>
    <apex:commandLink action="{!next}" rendered="{!hasNext}">Next</apex:commandlink>
    <apex:commandLink action="{!last}">Last</apex:commandlink>
    </apex:panelGrid>

  </apex:form>
</apex:page>

public with sharing class PagingController {

    List<cat3__c> categories {get;set;}

    // instantiate the StandardSetController from a query locator
    public ApexPages.StandardSetController con {
        get {
            if(con == null) {
                con = new ApexPages.StandardSetController(Database.getQueryLocator([Select Id, Name FROM Cat3__c Order By Name limit 100]));
                // sets the number of records in each page set
                con.setPageSize(5);
            }
            return con;
        }
        set;
    }

    public List<Cat3__c> getCategories() {
        categories = new List<Cat3__c>();
        for (Cat3__c category : (List<cat3__c>)con.getRecords())
            categories.add(category);

        return categories;
    }

    // displays the selected items
     public PageReference process() {
         for (Cat3__c cw : categories) {
             
                 ApexPages.addMessage(new ApexPages.message(ApexPages.severity.INFO,cw.name));
         }
         return null;
     }

    // indicates whether there are more records after the current page set.
    public Boolean hasNext {
        get {
            return con.getHasNext();
        }
        set;
    }

    // indicates whether there are more records before the current page set.
    public Boolean hasPrevious {
        get {
            return con.getHasPrevious();
        }
        set;
    }

    // returns the page number of the current page set
    public Integer pageNumber {
        get {
            return con.getPageNumber();
        }
        set;
    }

    // returns the first page of records
     public void first() {
         con.first();
     }

     // returns the last page of records
     public void last() {
         con.last();
     }

     // returns the previous page of records
     public void previous() {
         con.previous();
     }

     // returns the next page of records
     public void next() {
         con.next();
     }

     // returns the PageReference of the original page, if known, or the home page.
     public void cancel() {
         con.cancel();
     }

}