Is there is a maximum size for files that can be displayed in the native viewer?

No there are no restriction for native viewer , but in near native viewer we have chunk size to load.

<HtmlViewerOptions>

<SplitOptions><ChunkSize>15</ChunkSize></SplitOptions>

<ViewerDisplayOptions>

<RequestPartSize>5</RequestPartSize>

<DisplayPartSize>5</DisplayPartSize>

</ViewerDisplayOptions>

</HtmlViewerOptions>

The above value is found from:

select * from Tbl_Pj_ControlSetting where [key] = 'HTML_VIEWER_OPTIONS'