> For the complete documentation index, see [llms.txt](https://docs.viesus.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.viesus.com/use-cases/pdf-photobook-workflow.md).

# PDF Processing

**The scenario:** A print production platform receives photobook and catalogue PDFs from customers. Each PDF contains many embedded images at print-insufficient resolution. The platform needs to upscale and enhance every embedded image, then route the finished PDF to the print queue — automatically, as files arrive.

***

## Recommended interface

{% hint style="info" %}
Use the [**VIESUS PDF Enhancer**](/reference/pdf-cli.md) in **hotfolder mode**. It works directly on PDFs — enhancing the embedded images while preserving layout, text, and vector content — and can run unattended as a watched-folder service.
{% endhint %}

The PDF Enhancer is the only interface that operates inside PDFs. For standalone image files use the [CLI](/use-cases/photo-lab-batch.md); for an API-driven cloud flow that also handles PDFs, see [Cloud API Integration](/use-cases/cloud-api-integration.md).

***

## How it works

* A **hotfolder** watches an incoming directory. When a PDF lands, the enhancer analyses it, enhances (and optionally upscales) each qualifying embedded image to your target print resolution, and writes a new PDF to the output folder.
* Source files can be archived automatically, and a per-file XML report records how many images were processed, enhanced, or skipped — and an error code you can check before routing to print.
* It typically runs as a background service so the whole queue is processed without manual steps. A **standalone mode** is also available for one-off files or when you need to exclude specific pages.

***

## What to consider

| Factor                        | Guidance                                                                                                                                              |
| ----------------------------- | ----------------------------------------------------------------------------------------------------------------------------------------------------- |
| **Mode**                      | Hotfolder for continuous queues; standalone for one-off files or page exclusions.                                                                     |
| **Target resolution**         | Set the print DPI and cap the upscaling factor to avoid over-enlargement.                                                                             |
| **Classical vs AI upscaling** | Classical upscaling is fast and fine for most jobs; AI upscaling gives the best quality for premium products but needs an NVIDIA GPU and runs slower. |
| **Filtering**                 | Background fills and very small images can be skipped so only real photos are enhanced.                                                               |
| **GPU contention**            | Run one instance per GPU to avoid out-of-memory errors.                                                                                               |
| **Validation**                | Always check the XML report's error code before sending a PDF to the print queue.                                                                     |
| **Limitations**               | Password-protected PDFs can't be opened; very large PDFs need more memory.                                                                            |


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