[SalesForce] Uploading file via visualforce page error “Maximum view state size limit (135KB) exceeded”

I am trying to implement a page that I will upload files through it, but I keep having this error

Maximum view state size limit (135KB) exceeded. Actual view state size
for this page was 158.328KB

Here is my visualforce form

<apex:pageBlockSection columns="3">
    <apex:pageBlockSection >
      <apex:pageBlockSectionItem >
         <apex:inputFile value="{!document.body}" filename="{!document.name}" id="file"/> 
     </apex:pageBlockSectionItem>  
     <apex:pageBlockSectionItem >
        <apex:outputLabel value="Description" for="description"/>
        <apex:inputTextarea value="{!document.description}" id="description"/>
     </apex:pageBlockSectionItem>
 </apex:pageBlockSection>
 </apex:pageBlockSection>
 <apex:pageBlockButtons >
    <apex:commandButton action="{!upload}" value="Upload"/>
 </apex:pageBlockButtons>

and here is my APEX code

public List<Document> documents{set;get;}
public Document document 
{
  get 
  {
    if (document == null)
      document = new Document();
      return document;
  }
  set;
}
document.AuthorId = UserInfo.getUserId();
    document.FolderId = account.ID;
    try {
       insert document;
    } catch (DMLException e) {
       ApexPages.addMessage(new ApexPages.message(ApexPages.severity.ERROR,'Error'));
    } finally {
       document.body = null;
       document = new Document();
       documents = [SELECT Query];
    }

What is the problem here ?

Update: The query was like this

documents = [SELECT Description, body, Id, Name, Url FROM Document WHERE
AuthorId =:UserInfo.getUserId()];

but it works after I removed body

documents = [SELECT Description, Id, Name, Url FROM Document WHERE
AuthorId =:UserInfo.getUserId()];