I have an open document text file with some images anchored as character: the total size of all images is about 2.4 MB, each image is put within the first row a two-rows table with no borders, while the second row of this table contains a text as the caption for the image; the size of this ODT file is about 2.5 MB.
So, when I export this document to PDF/A, using a compression level of 90%, the size of the resulting PDF file is about 2.9 MB.
Then, I have modified only the image anchoring of all images in the above document, so all the images are anchored to page: in order to add a caption to each image, I have chosen Insert - Caption for each image; the size of the resulting ODT file is about the same as above.
But, when I export this document to PDF/A, using the same export settings as above, the size of the resulting PDF file is about 13.9 MB.
Why does the second document produce a bigger PDF file?
After making some tests, I found that the problem might be caused by the captions: if I do not insert a caption to the images, then the size of the resulting PDF file does not excessively increases in size.
How to solve the problem?