,,,,,

In the XML the following can be observed.

    font-size: 1e-32px;

This is very, very small and not visible though if you select the text in the object list it does get selected and it is possible to EDIT the XML value or ADD Inkscape text styling to the element and it will be displayed. When viewing the XML we see the Inkscape styling is added to the text-id object but the damaged styling is in one of the tags one level down but before the text string.

My case is not a non-Latin OS, a pretty vanilla MacOS 15.3 with US and/or UK, FIN settings. I loaded the latest stable InkScape onto my colleagues laptop so they could try and edit a single PDF file.  There seems to be few open-source PDF editors that will allow actual real editing.  While all the lines and embedded graphic show up correctly on Inkscape the loss of text makes it unusable.  If there was a way to parse a PDF and hack it so this bug was not triggered then I suppose that would be fine.
,,,,,
 

.....

Also the funny thing was that in my case one text string out of about 60 strings was displayed correctly.  Also I am not sure if the bold styling was lost or if a bold font was used but when I edit the error in the XML file for font-size the text is correctly displayed but the weight is not.

A very similar fault is discussed in the following GitLab error that is just over a year old.
gitlab . com/inkscape/inkscape/-/issues/4845

I regret that I am unable to provide a sample file until I can edit out the customer details and this would require a working PDF editor.

=====
It seems to be working, I find it hard to believe I can only post a couple of paragraphs at a time.

Regards

Kalle
--
Helsinki, Finland