Yes, the PDF-Tools SDK supports low-level API. This feature and others, such as the creation and editing of Adobe Acroforms and digital signatures, requires a full PDF-XChange PRO SDK license. Free and fully-functioning demos of our SDK products are available here.
Please note that the low-level API is a powerful set of functions that enables developers to make changes at the most fundamental level of PDF files. Whilst this is very useful from a developmental perspective, indiscriminate use will undoubtedly lead to file corruption and other issues. PDF XChange will not accept any responsibility, should such problems arise, and we advise emphatically that developers exercise caution and patience when the low-level API is utilized.
If you request support in relation to the low-level API then we will expect you to have a thorough working knowledge of PDF and the associated Adobe documentation. The best reference for this is:
This documents provide a comprehensive description/analysis of PDF and are intended for developers of PDF-related software. It contain sufficient information to enable developers to write applications that read PDF files and/or modify their content.