Magento – M2: How to add store address to transactional email / invoice email

For logo:

There is an email var for that:

{{skin url="images/logo_email.gif" _area='frontend'}}

To make it your own, upload and replace logo_email.gif

For email variables:

Some of these exist by default:

General Store Email address:

{{config path="trans_email/ident_general/email"}}

Store Name:

{{config path="general/store_information/name"}}

Store Code is trickier. This is not exposed in the config to my knowledge for use by the email templates. I suggest using a custom template file, and refer this way:

{{block type="core/template" template="custom/storecode.phtml"}}

storecode.phtml:

<?php

echo Mage::app()->getStore()->getCode();

Alternatively, and maybe less-desirable, are Custom Variables.

Custom Variables

System > Custom Variable > Add New Variable

To Implement a custom variable into a Transactional Email, do the following: In the Admin Panel, select System > Transactional Emails Click the row of predefined template to edit or click [Add New Template] button to create a new one. Create a new transactional email first if needed. In the Template Content field, select a location for your custom variable. Click [ Insert Variable ] and select the Custom Variable you would like to insert.

_{Source: http://www.magentocommerce.com/knowledge-base/entry/creating-custom-variables}

You can get the customer email like this in the invoice or order templates:

{{var order.getCustomerEmail()}}

SO you can try to add

Email: {{var order.getCustomerEmail()}}

after

{{var order.shipping_address.format('html')}}

[Edit]
For pdf you should replace this from Mage_Sales_Model_Order_Pdf_Abstract::insertOrder

$shippingAddress = $this->_formatAddress($order->getShippingAddress()->format('pdf'));

with

$shippingAddress = $this->_formatAddress($order->getShippingAddress()->format('pdf').'|'.Mage::helper('sales')->__('Email:').$order->getCustomerEmail());  

Of course you shouldn't edit the core code.
You have to copy the file to the local folder. You cannot do a simple override because it's an abstract class.