A key feature of the webonboarding product is the ability to upload DOCX templates. These templates are then merged with onboardee personal data along with job offer data and the output is converted to PDF for review and signing. After extensive research and development, we chose Aspose.Words for Java as a vital building block in the document generation process.

One challenge in implementing this feature was finding a reliable way of converting the generated DOCX file to PDF. Our requirements were:

1. Fidelity: The output PDF file needs to match the input DOCX as closely as possible. This includes fonts and the ability to convert more irregular DOCX features such as tables and text boxes.
2. Speed: The application should generate single documents as well as bulk documents in the thousands, in a reasonable amount of time.
3. Reliability: The process needs to run successfully regardless of the input document.

We implemented a trial version of Aspose.Words for Java and were astonished at the improved speed performance, reliability and quality of the output document.Key improvements:

1. Fidelity: Aspose has been able to convert all the DOCX features we have tested, maintaining document layout and appearance. Aspose correctly converts documents with embedded fonts. For non-embedded fonts, Aspose uses the correct fonts if present on the server and provides a mechanism for defining specific fall-back fonts for metric compatibility.
2. Speed: On a bulk generation of 1,000 documents, Aspose has cut the generation by one third, when compared to our previous implementation on the same environment with a similar system load.
3. Reliability: Aspose has been able to reliably convert every DOCX document we have tested even complex and large documents, and is able to convert documents with embedded fonts.

After extensive research and testing we decided to go with the Aspose.Words for Java library for converting DOCX documents to PDF. The library is robust, fast and produces high quality PDF files matching the input DOCX formatting and layout. The library is flexible and may be used for more tasks throughout the system in the future.