more info https://processwire.com/talk/topic/371-page-specific-permissions/?p=2787.

CustomPageRoles.module

<?php

// Module from ryan....

class CustomPageRoles extends WireData implements Module {

	/**
	 * Provide information about this module to ProcessWire
	 *
	 */
	public static function getModuleInfo() {
		return array(
			'title' => 'Custom Page Roles', 
			'summary' => 'Control viewable roles at the page level.', 
			'version' => 002, 
			'permanent' => false, 
			'autoload' => true, 
			'singular' => true, 
			);
	}

	/**
	 * Add the hook
	 *
	 */
	public function init() {
		$this->addHookAfter("Page::viewable", $this, 'viewable');
	}

	/**
	 * Hook called after Page::viewable is called
	 *
	 */
	public function viewable(HookEvent $event) {

		// get the vars we need to check access
		$page = $event->object; 
		$user = $this->user; 

		// no need to check anything if it's the superuser
		if($user->isSuperuser()) return; 

		// don't allow this access control on system templates
		if($page->template->flags & Template::flagSystem) return; 

		// get the roles we'll be comparing
		$pageRoles = $page->page_roles; 
		$userRoles = $this->user->roles; 

		// if page doesn't have a 'page_roles' field, then return control to template
		if(is_null($pageRoles) || (!$pageRoles instanceof PageArray)) return; 

		// if page has a 'page_roles' field, but none defined, then inherit 'viewable' state from template or parent
		if(!count($pageRoles)) {

			// if template disallows access give it control. 
			if(!$event->return) return; 

			// if there is no parent, give the template control. 
			if(!$page->parent->id) return; 

			// if the parent has no page_roles field, then give the template control.
			if(is_null($page->parent->page_roles)) return; 

			// otherwise determine access from page's parent, recursively 
			$event->return = $page->parent->viewable(); 
			return; 
		}

		// we assume it's not viewable until we can prove otherwise
		$viewable = false; 

		// loop through the pageRoles and try to match up to user
		// we don't need to check permissions in the role because
		// all roles are assumed to have page-view permission. 
		foreach($pageRoles as $role) {
			if($role->name == 'guest' || $user->hasRole($role)) {
				// guest role was found or the user has the required role
				$viewable = true; 
				break;
			}
		}	

		$event->return = $viewable;
	}

	/**
	 * Install the module
	 *
	 */
	public function ___install() {

		if($this->fields->get('page_roles')) {
			$this->error("You already have a 'page_roles' field."); 
			return;
		}

		$field = new Field();
		$field->type = $this->modules->get("FieldtypePage"); 
		$field->name = 'page_roles';
		$field->label = 'Roles that can view this page';	
		$field->description = 
			"Check the roles that may view this page. At least one role must be checked (like one of your roles or superuser), " . 
			"otherwise this page does not define access. When access is not defined here, it is inherited from the template " . 
			"or parent(s). If this page's template allows 'view' access to the user, then it will check the parent(s). " . 
			"Access will inherit from parents that also have a custom page roles field. ";
		$field->derefAsPage = 0;
		$field->parent_id = $this->config->rolesPageID; 
		$field->labelFieldName = 'name';
		$field->inputfield = 'InputfieldCheckboxes';
		$field->save();

		$this->message("Added field 'page_roles'. Add this field to any templates where you want to control view access."); 
	}

	/**
	 * Uninstall the module
	 *
	 */
	public function ___uninstall() {
		$this->message("To complete uninstall, remove the 'page_roles' field from all templates and then delete the 'page_roles' field."); 
	}
}