When you are converting Visio files, you can choose what you want to render: Visio scheme pages or figures of Visio scheme. If Visio scheme does not contain pages - only figures will be rendered.
To force render Visio figures please set RenderFiguresOnly property to true in VisioRenderingOptions. You can set width of each figure, height will be calculated by proportions automatically.
API Usage There are steps that usage of GroupDocs....Acquisition GroupDocs Cloud Documentation / GroupDocs.Viewer Cloud...options by document type / Rendering Visio Documents / Render Visio...