Comment 8 for bug 1004887

The black rectangles around the PNG graphics in your exported PDF are likely caused by a bug in Inkscape version 0.48.2. This bug has been fixed in later versions of Inkscape, so I recommend upgrading to the latest version if possible.

In the meantime, there are a few workarounds you can try:

Export your PDF to a different format. For example, you could export to PNG or EPS and then convert that file to PDF using a different program.
Use a different PDF exporter. There are a number of third-party PDF exporters available for Inkscape, such as CairoSVG and Ghostscript.
Manually remove the black rectangles. You can do this using a PDF editor such as Adobe Acrobat or Inkscape itself.
If you choose to manually remove the black rectangles, here are the steps involved:

Open the PDF in Inkscape.
Select the black rectangle around the PNG graphic.
Press the Delete key.
Repeat steps 2 and 3 for all of the black rectangles in your PDF.
Save your PDF.
Here are some additional tips for exporting PDFs from Inkscape:

Make sure that all of your objects are embedded in the PDF. To do this, go to File > Document Properties > Embed Fonts and Images.
Set the PDF version to 1.4 or higher. This will ensure that your PDF is compatible with a wide range of software.
Use a high resolution (e.g. 300 dpi) for best results. by
I hope this helps!https://www.ufabetwins.ai/