It is very likely that the imported PDF texts are still in the form of CAD line segments, and you can choose to transform them into identifiable texts through "Identify PDF Text".
Step 1, select the target PDF text, right click to confirm;
Step 2, a dialog window pops out, showing the identification result. The original text is displayed at the
bottom of the window, where you can have a clear comparison with the identified data.
"Create Text Entity" controls whether to generate identifiable text type;
"Delete Original Lines" controls whether to delete the line segments in the PDF texts