PDF Crowd MODX Plugin. Using the API from PDF Crowd, this plugin will convert a MODX resource in to PDF format and then save it to your web server in a specified location.

pdfcrowd.plugin.php

<?php
/**
 * PDF Crowd MODX Plugin
 * 
 * Using the API from PDF Crowd, this plugin will convert a MODX resource in to 
 * PDF format and then save it to your web server in a specified location.
 * 
 * The plugin is setup to trigger witin a certain MODX context. 
 * For example, a "pdf" context.
 * 
 * To use this plugin, you will need a username and API key which is available from:
 * https://pdfcrowd.com/user/sign_up/?pid=api-trial
 * 
 * You will also need to download the php class and place it in:
 * /assets/components/pdfcrowd/pdfcrowd.php
 * 
 * Events: OnDocFormSave
 *
 * @author Jon Leverrier <jon@youandmedigital.com>
 * version: 0.1
 *
 */
$eventName = $modx->event->name;
switch($eventName) {
    case 'OnDocFormSave':
        
        // load some default settings
        $pdfc_user = 'xxx';
        $pdfc_key = '123';
        $target_context = 'pdf';
        $pdf_dir = 'pdf/';
        
        // get current time to append to file name
        $date_stamp = date('-dmY');
        // get the current page id
        $id = (!empty($id) ? $id : $modx->resource->get('id'));
        // make a full url from resource id
        $target_url = $modx->makeUrl($id,'','','https');
        // get modResource object
        $current_resouceid = $modx->getObject('modResource', $id);
        // get current context_key from modResource object
        $current_context = $current_resouceid->get('context_key');
        // get current alias from modResource object
        $current_alias = $current_resouceid->get('alias');
            
        // if current_context is target_context do something, if not do nothing
        if ($current_context == $target_context){
            
            require MODX_ASSETS_PATH . 'components/pdfcrowd/pdfcrowd.php';
            
            try
            {
                // create the API client instance
                $client = new \Pdfcrowd\HtmlToPdfClient($pdfc_user, $pdfc_key);
            
                // run the conversion and write the result to a file
                $client->convertUrlToFile($target_url, MODX_ASSETS_PATH . $pdf_dir . $current_alias . $date_stamp . ".pdf");
            }
            catch(\Pdfcrowd\Error $why)
            {
                // report the error to modx error log
                $modx->log(modx::LOG_LEVEL_ERROR,'[ PDF Crowd ]' . $why);
            }
        } 
        else {
            // do nothing
            return;
        }
    
    break;
}