Bug description:

When an Excel workbook contains text inside Text Box objects, the text from those Text Boxes is duplicated many times when copied from the resulting PDF in Adobe Acrobat.

The issue only affects text contained in Excel Text Box objects. Normal text in Excel cells does not have this problem.

Steps to reproduce:

Open Microsoft Excel on Windows.
Create a worksheet containing normal text in a cell.
Insert a Text Box and enter some text into it.
Export the worksheet to PDF using Excel's Save as PDF function.
Open the resulting PDF in Adobe Acrobat.
Select the text, or press Ctrl+A and then Ctrl+C.
Paste the copied content into Notepad or another plain-text editor.

Actual result:

The text contained in the Excel Text Box is repeated many times in the pasted result.

Normal cell text is copied correctly without duplication.

Expected result:

Each Text Box text should appear only once when copied from the PDF.

Additional observations:

The PDF visually displays the Text Box text correctly. There is no visible duplication on the page.
Microsoft Edge's built-in PDF viewer can copy the same PDF correctly without producing the duplicated text.
The problem occurs specifically when the PDF is opened in Adobe Acrobat and the text is copied.
The problem is reproducible with Microsoft Excel 2019.
The problem is also reproducible with Microsoft Excel 2021.
The problem has been reproduced on multiple Windows computers.
Both Excel's F12 / Save As PDF workflow and File > Save As > PDF produce PDFs with the same issue.
The issue appears to be specific to text generated from Excel Text Box / Shape objects, rather than normal worksheet cell text.

This suggests that the PDF may contain multiple or overlapping text objects for the same Text Box content, and Acrobat's text selection/copy engine may be extracting those objects repeatedly even though they are visually rendered as a single piece of text.

This is particularly problematic because Excel's F12 Save As workflow is a fast and frequently used way to create PDFs, and the resulting PDFs should allow the Text Box content to be copied normally.