Compile Error: Illegal assignment from System.PageReference to pagereference

attachementPDF Page

<apex:page standardController="account" renderAs="PDF">
    <c:attachment />
</apex:page>


sendemail Page

<apex:page controller="sendEmail">
    <apex:messages />
    <apex:pageBlock title="Send an Email to Your 
            {!account.name} Representatives">
        <p>Fill out the fields below to test how you might send an email to a user.</p>
        <br />
        <apex:dataTable value="{!account.Contacts}" var="contact" border="1">
            <apex:column >
                <apex:facet name="header">Name</apex:facet>
                {!contact.Name}
            </apex:column>
            <apex:column >
                <apex:facet name="header">Email</apex:facet>
                {!contact.Email}
            </apex:column>
        </apex:dataTable>
    
        <apex:form >
        <br /><br />
            <apex:outputLabel value="Subject" for="Subject"/>:<br />     
            <apex:inputText value="{!subject}" id="Subject" maxlength="80"/>
            <br /><br />
            <apex:outputLabel value="Body" for="Body"/>:<br />     
            <apex:inputTextarea value="{!body}" id="Body"  rows="10" cols="80"/>           
            <br /><br /><br />
            <apex:commandButton value="Send Email" action="{!send}" /> 
        </apex:form>
    </apex:pageBlock>
    <apex:pageBlock title="Preview the Attachment for {!account.name}">
        <c:attachment />
</apex:pageBlock>
</apex:page>

attachement component

<apex:component access="global">
    <apex:detail relatedList="false" title="false"/>
</apex:component>


send email controller


public class sendEmail {
    public String subject { get; set; }
    public String body { get; set; }

    private final Account account;

    // Create a constructor that populates the Account object 
    
    public sendEmail() {
        account = [SELECT Name, 
                  (SELECT Contact.Name, Contact.Email FROM Account.Contacts) 
                   FROM Account 
                   WHERE Id = :ApexPages.currentPage().getParameters().get('id')];
    }

    public Account getAccount() {
        return account;
    }

    public PageReference send() {
        // Define the email 
    
        Messaging.SingleEmailMessage email = new Messaging.SingleEmailMessage(); 

        // Reference the attachment page and pass in the account ID
        PageReference pdf =  Page.attachmentPDF;
        pdf.getParameters().put('id',(String)account.id); 
        pdf.setRedirect(true);

        // Take the PDF content
        Blob b = pdf.getContent();

        // Create the email attachment
        Messaging.EmailFileAttachment efa = new Messaging.EmailFileAttachment();
        efa.setFileName('attachment.pdf');
        efa.setBody(b);

        String addresses;
        if (account.Contacts[0].Email != null) {
            addresses = account.Contacts[0].Email;
            // Loop through the whole list of contacts and their emails 
    
            for (Integer i = 1; i < account.Contacts.size(); i++) {
                if (account.Contacts[i].Email != null) {
                    addresses += ':' + account.Contacts[i].Email;
                }
            }
        }

        String[] toAddresses = addresses.split(':', 0);

        // Sets the paramaters of the email 
    
        email.setSubject( subject );
        email.setToAddresses( toAddresses );
        email.setPlainTextBody( body );

        email.setFileAttachments(new Messaging.EmailFileAttachment[] {efa}); // Sends the email 
    
        Messaging.SendEmailResult [] r = 
            Messaging.sendEmail(new Messaging.SingleEmailMessage[] {email});   
		
        return null;
    }
}