How to change Pdf logo in Magento

Login into the Magento admin panel

Select System -> Configuration -> Sales

In that select the Invoice and Packing Slip Design. In that upload the logo images.

how to change pdf font & styles in magento

All the Pdf which are related to the order is available in the following location.

/app/code/local/Mage/Sales/Model/Order/Pdf/

We can edit the invoice pdf font & styles in magento. Please follow the below inorder to successed the changes.

Page format: The default invoice PDF is set up in the A4 format. To set it for letter in /app/code/core/Mage/Sales/Model/Order/Pdf/Invoice.php

change

$page = $pdf->newPage(Zend_Pdf_Page::SIZE_A4);

to

$page = $pdf->newPage(Zend_Pdf_Page::SIZE_LETTER);