diff --git a/readme.md b/readme.md
index 97a2864..b4c2807 100644
--- a/readme.md
+++ b/readme.md
@@ -1,13 +1,13 @@
 <p align="center">
     <img src="https://raw.githubusercontent.com/themsaid/ibis/master/art/cover.png" alt="Ibis logo" width="480">
-    
+
 Artwork by <a href="https://twitter.com/ericlbarnes">Eric L. Barnes</a> and <a href="https://twitter.com/Caneco">Caneco</a> from <a href="https://laravel-news.com/ibis-book-maker">Laravel News</a> ❤️.
 </p>
 
 ---
 
 This PHP tool helps you write eBooks in markdown. Run `ibis build` and an eBook will be generated with:
- 
+
 1. A cover photo.
 2. Clickable auto-generated table of contents.
 3. Code syntax highlighting.
@@ -45,7 +45,7 @@ You may configure your book by editing the `/ibis.php` configuration file.
 
 ## Writing Your eBook
 
-The `init` command will create sample .md files inside the content folder. You can explore those files to see how you can write your book. This sample content is taken from [Laravel Queues in Action](https://learn-laravel-queues.com). 
+The `init` command will create sample .md files inside the content folder. You can explore those files to see how you can write your book. This sample content is taken from [Laravel Queues in Action](https://learn-laravel-queues.com).
 
 Inside the content directory, you can write multiple `.md` files. Ibis uses the headings to divide the book into parts and chapters:
 
@@ -61,7 +61,7 @@ Inside the content directory, you can write multiple `.md` files. Ibis uses the
 ### Starting with Ibis
 
 <h3> tags define different titles inside a chapter.
-``` 
+```
 
 ## Using Fonts
 
@@ -91,6 +91,30 @@ ibis sample dark
 
 This command will use the generated files from the `ibis build` command to generate samples from your PDF eBook. You can configure which pages to include in the sample by updating the `/ibis.php` file.
 
+
+## Extending Ibis
+
+### Build lifecycle hooks
+
+You can customize your Ibis build process by defining lifecycle hook function(s) in your `ibis.php` config;
+
+```php
+return [
+
+	'prehtml' => function($markdown) {
+	    // preprocesses markdown content before converting to HTML
+	    return $markdown;
+	},
+
+	'prepdf' => function($html) {
+	    // preprocesses converted markdown HTML content before writing to PDF
+	    return $html;
+	},
+
+    // .. rest of ibis.php config
+];
+```
+
 ## Credits
 
 - [Mohamed Said](https://github.com/themsaid)
diff --git a/src/Commands/BuildCommand.php b/src/Commands/BuildCommand.php
index 25a602c..0078366 100644
--- a/src/Commands/BuildCommand.php
+++ b/src/Commands/BuildCommand.php
@@ -33,6 +33,12 @@ class BuildCommand extends Command
      */
     private $disk;
 
+    /**
+     * User ibis.php config settings
+     * @var array
+     */
+    private $_config;
+
     /**
      * Configure the command.
      *
@@ -62,7 +68,7 @@ public function execute(InputInterface $input, OutputInterface $output)
         $this->themeName = $input->getArgument('theme');
 
         $currentPath = getcwd();
-        $config = require $currentPath.'/ibis.php';
+        $this->_config = require $currentPath.'/ibis.php';
 
         $this->ensureExportDirectoryExists(
             $currentPath = getcwd()
@@ -72,7 +78,6 @@ public function execute(InputInterface $input, OutputInterface $output)
 
         $this->buildPdf(
             $this->buildHtml($currentPath.'/content'),
-            $config,
             $currentPath,
             $theme
         );
@@ -107,6 +112,10 @@ protected function buildHtml(string $path)
     {
         $this->output->writeln('<fg=yellow>==></> Parsing Markdown ...');
 
+        if (is_callable($this->_config['prehtml'] ?? null)) {
+            $this->output->writeln('<fg=yellow>==></> Pre-processing Markdown ...');
+        }
+
         $environment = Environment::createCommonMarkEnvironment();
 
         $environment->addBlockRenderer(FencedCode::class, new FencedCodeRenderer([
@@ -125,6 +134,12 @@ protected function buildHtml(string $path)
                     $file->getPathname()
                 );
 
+
+                if (is_callable($this->_config['prehtml'] ?? null)) {
+                    $markdown = $this->_config['prehtml']($markdown);
+                }
+
+
                 return $this->prepareForPdf(
                     $converter->convertToHtml($markdown),
                     $i + 1
@@ -160,13 +175,12 @@ private function prepareForPdf(string $html, $file)
 
     /**
      * @param  string  $html
-     * @param  array  $config
      * @param  string  $currentPath
      * @param  string  $theme
      * @throws \Illuminate\Contracts\Filesystem\FileNotFoundException
      * @throws \Mpdf\MpdfException
      */
-    protected function buildPdf(string $html, array $config, string $currentPath, string $theme)
+    protected function buildPdf(string $html, string $currentPath, string $theme)
     {
         $defaultConfig = (new ConfigVariables())->getDefaults();
         $fontDirs = $defaultConfig['fontDir'];
@@ -176,13 +190,13 @@ protected function buildPdf(string $html, array $config, string $currentPath, st
 
         $pdf = new Mpdf([
             'mode' => 'utf-8',
-            'format' => $config['document']['format'] ?? [210, 297],
-            'margin_left' => $config['document']['margin_left'] ?? 27,
-            'margin_right' => $config['document']['margin_right'] ?? 27,
-            'margin_bottom' => $config['document']['margin_bottom'] ?? 14,
-            'margin_top' => $config['document']['margin_top'] ?? 14,
+            'format' => $this->_config['document']['format'] ?? [210, 297],
+            'margin_left' => $this->_config['document']['margin_left'] ?? 27,
+            'margin_right' => $this->_config['document']['margin_right'] ?? 27,
+            'margin_bottom' => $this->_config['document']['margin_bottom'] ?? 14,
+            'margin_top' => $this->_config['document']['margin_top'] ?? 14,
             'fontDir' => array_merge($fontDirs, [getcwd().'/assets/fonts']),
-            'fontdata' => $this->fonts($config, $fontData),
+            'fontdata' => $this->fonts($fontData),
         ]);
 
         $pdf->SetTitle(Ibis::title());
@@ -207,8 +221,8 @@ protected function buildPdf(string $html, array $config, string $currentPath, st
         } else {
             $this->output->writeln('<fg=yellow>==></> Adding Book Cover ...');
 
-            $coverPosition = $config['cover']['position'] ?? 'position: absolute; left:0; right: 0; top: -.2; bottom: 0;';
-            $coverDimensions = $config['cover']['dimensions'] ?? 'width: 210mm; height: 297mm; margin: 0;';
+            $coverPosition = $this->_config['cover']['position'] ?? 'position: absolute; left:0; right: 0; top: -.2; bottom: 0;';
+            $coverDimensions = $this->_config['cover']['dimensions'] ?? 'width: 210mm; height: 297mm; margin: 0;';
 
             $pdf->WriteHTML(
                 <<<HTML
@@ -223,6 +237,12 @@ protected function buildPdf(string $html, array $config, string $currentPath, st
 
         $pdf->SetHTMLFooter('<div id="footer" style="text-align: center">{PAGENO}</div>');
 
+
+        if (is_callable($this->_config['prepdf'] ?? null)) {
+            $this->output->writeln('<fg=yellow>==></> Pre-processing PDF ...');
+            $html = $this->_config['prepdf']($html);
+        }
+
         $this->output->writeln('<fg=yellow>==></> Building PDF ...');
 
         $pdf->WriteHTML(
@@ -254,9 +274,9 @@ private function getTheme($currentPath, $themeName)
      * @param $fontData
      * @return array
      */
-    protected function fonts($config, $fontData)
+    protected function fonts($fontData)
     {
-        return $fontData + collect($config['fonts'])->mapWithKeys(function ($file, $name) {
+        return $fontData + collect($this->_config['fonts'])->mapWithKeys(function ($file, $name) {
             return [
                 $name => [
                     'R' => $file
diff --git a/stubs/ibis.php b/stubs/ibis.php
index c5474cc..2abb286 100644
--- a/stubs/ibis.php
+++ b/stubs/ibis.php
@@ -1,5 +1,22 @@
 <?php
 
+
+if (!function_exists('prehtml')) {
+function prehtml($markdown) {
+    // preprocesses markdown content before converting to HTML
+    return $markdown;
+}
+}
+
+
+if (!function_exists('prepdf')) {
+function prepdf($html) {
+    // preprocesses converted markdown HTML content before writing to PDF
+    return $html;
+}
+}
+
+
 return [
     /**
      * The book title.
@@ -56,6 +73,6 @@
     /**
      * A notice printed at the final page of a generated sample.
      */
-    'sample_notice' => 'This is a sample from "Laravel Queues in Action" by Mohamed Said. <br> 
+    'sample_notice' => 'This is a sample from "Laravel Queues in Action" by Mohamed Said. <br>
                         For more information, <a href="https://www.learn-laravel-queues.com/">Click here</a>.',
 ];