Many organizations need to capture print jobs from Windows applications and convert them into PDF for record-keeping, compliance, or workflow automation. This requirement is common in industries such as finance, insurance, healthcare, and enterprise IT, where paper-based printouts must be digitally archived.
A typical challenge is that Windows spool files (SPL files) are not uniform. Their format depends on the printer driver in use:
- PostScript (PS)
- Printer Command Language (PCL)
- XML Paper Specification (XPS)
- Enhanced Metafile (EMF)
- Encapsulated PostScript (EPS)
Because of these variations, a robust solution must both capture spool files reliably and convert them into PDF consistently.
This article explains the available VeryPDF solutions, their roles, and how to choose the right combination for your project.
![[Solution] Choosing the Right VeryPDF SDK for SPL-to-PDF Conversion and Print Job Capture](https://www.verypdf.com/wordpress/wp-content/uploads/2025/08/image-14.png "[Solution] Choosing the Right VeryPDF SDK for SPL-to-PDF Conversion and Print Job Capture")
The $1500 Virtual Printer SDK: What It Can and Cannot Do
The PDF Virtual Printer SDK Based on Postscript Printer Driver is often the first product developers notice.
https://veryutils.com/pdf-virtual-printer
What It Does
- Provides a virtual PDF printer that can be installed on a system.
- Applications can “print” directly into PDF using this driver.
- Allows integration into software products that need a PDF output option.
What It Does Not Do
- Does not capture spool files directly from the Windows spooler.
- Does not provide HookPrinter functionality.
- Does not handle SPL-to-PDF conversion.
- Does not include watermarking, stamping, or batch automation features.
Conclusion: If your requirement is only to install a virtual printer that outputs PDF, this SDK is enough. But if you need to monitor and capture print jobs silently in the background and convert them to PDF, you must look at other SDKs.
Complete Solution for SPL Capture and Conversion
For end-to-end handling of spool files, two products work together:
1. VeryPDF HookPrinter SDK
- Monitors the Windows print spooler at the system level.
- Automatically intercepts spool files when a user or application sends a job to a printer.
- Works invisibly in the background without requiring user interaction.
- Exposes an API for developers (C#, C++, etc.) to capture job data.
https://www.verypdf.com/app/hookprinter/try-and-buy.html#hookprinter-sdk
Use Case Example:
Your C# Windows Service runs in the background. When a user prints from Word or Excel, HookPrinter captures the SPL file before it reaches the physical printer. Your service can then decide whether to save, convert, or forward the job.
2. VeryPDF SPL to PDF Converter Command Line
- Converts SPL files into PDF reliably.
- Supports multiple spool formats (PS, PCL, XPS, EMF, EPS).
- Runs as a command-line tool, making it easy to call from Windows Services, batch files, or APIs.
- Produces high-quality PDFs suitable for archiving, sharing, or further processing.
https://www.verypdf.com/app/hookprinter/try-and-buy.html#spl-to-pdf-cmd
Use Case Example:
Your C# service calls spl2pdf.exe with the intercepted SPL file. The tool converts it to PDF silently, and your service saves the result to a database or forwards it to another system.
Why Both Are Needed
- HookPrinter SDK = Capturing mechanism (collects spool files).
- SPL to PDF Converter = Transformation engine (converts spool to PDF).
Without HookPrinter, you would have to manually fetch SPL files from spooler folders.
Without SPL to PDF Converter, you cannot transform them into usable PDFs.
Optional Add-On Features
Depending on your workflow, you might also need:
- PDF Stamp SDK / Command Line
- Add watermarks, timestamps, user IDs, or IP addresses.
- Useful for compliance or tracking distribution.
- PDFPrint SDK / Command Line
- Print the converted PDFs to physical printers.
- Offers advanced control over print settings.
These tools can be chained together with HookPrinter and SPL-to-PDF to build powerful automated workflows.
Integration and Deployment
For Developers
- All SDKs and command-line tools can be called from C# Windows Services or other .NET applications.
- Integration can be done via process invocation (
Process.Start) or DLL imports (for SDK versions). - No user interaction is required once integrated.
For Deployment
- The tools can be silently bundled into your installer.
- End-users will not need to install VeryPDF software separately.
- With the developer license, you may redistribute the tools royalty-free.
This makes it possible to embed VeryPDF’s technology into your own commercial software solutions.
Example Workflow
- A user prints a document in Word → job sent to printer spooler.
- HookPrinter SDK captures the spool file (
.spl). - Your service calls
spl2pdf.exeto convert the file into PDF. - Optional: Apply watermark or text stamp (timestamp, IP, user ID).
- Optional: Auto-print the final PDF to another printer.
- Store or forward the PDF for record-keeping.
This workflow is ideal for:
- Document management systems
- Audit/compliance archives
- Insurance or banking systems
- Healthcare records management
- Secure enterprise print monitoring
Conclusion
If your project requires only a virtual PDF printer, the Virtual Printer SDK is sufficient.
But if you require a complete SPL capture and PDF conversion solution, you will need both:
- HookPrinter SDK (for capturing jobs)
- SPL to PDF Converter (for transforming SPL into PDF)
Additional features such as watermarking and PDF printing can be added with separate SDKs.
* VeryPDF PDF Stamp Command Line or SDK (for watermarking/text stamping)
https://www.verypdf.com/app/pdf-stamp/try-and-buy.html
* VeryPDF PDFPrint Command Line or SDK (for automated PDF printing)
https://www.verypdf.com/app/pdf-print-cmd/
This modular approach lets you build a solution tailored to your needs, from simple PDF printing to full enterprise-grade print job management and PDF archiving.