You can fetch a specific document by specifying its key.
fetchDocument() returns one instance of
Zend_Cloud_DocumentService_Document.
Example 80. Fetching a document
<?php
$document = $service->fetchDocument('collectionName', 'DocumentID');
echo "Document ID: " . var_export($document->getID(), 1) . "\n";
foreach ($document->getFields() as $key => $value) {
echo "Field $key is $value\n";
}