I looked at the first file only. It has "in verde lo" at the bottom which is unseen.
/F2 14 Tf
[(in v)20(er)40(de l)2(o )]TJ
.77 -.252 62.09 10.22 re
62.88 0 0 11.04 .29 -.732 cm
It is rendered in mode 7 (Add text to path for clipping = NEITHER_CLIP). I.e. the path of the text is used to clip a part of a mostly black image (/I4).
Changing the TJ line to
shows the text, although in poor quality. This looks to me as if adding the shapes to the clipping path doesn't work properly for TJ if there are several elements.
John Hewson In PageDrawer.showText(), the textClippingArea is reset at the beginning of each call, and at the end, state.intersectClippingPath(textClippingArea); is called. So if showText() is called several times as it is done in TJ, the intersection would be empty