viceant wrote:I want to change to grayscale all the pictures in all pages of a file simultaneously
You can do that, if all the
shapes have been connected to default style (usually light blue / blue classic filling/area). Hit F11 key (styles & formatting) and select a shape. Then rightclick the default style and ... change in a greyscale colour. Done.
This only will work, if you had not changed any single shape by hard formatting. Hard formatted shapes can't be changed by the above described way. The only way is to update the default style as often as you have got different fillings (rightclick shape and click "update style"); then also former hard formatted shapes are included in changes of styles.
Next time use styles and it will work easier.
All that does not work for
bitmap objects. Do you have to change their colours too?
"select all" on the menu donesn't select images that seem to be in the background
There are layers. Probably one or more of them are locked. In this case you have to unlock before. To find out these locked objects the
navigator (click F5 key) may be helpful.
Or some bitmap/hatching/gradient/colour is part of the page background. You have to edit page properties.
I intend to do it in pdf files made by a scanner
Not bad, the better idea is
to print out as PDF files. Before you do that choose color Grayscale in printer dialogue. How can you do that? Install a PDF printer and you will have an additional choice in your printer dialog. The pdf printer prints out not as a paper(s) but as a pdf file(s). Don't forget that this is a conversion and each of your shapes won't be editable as shapes but as some curve objects.
Why do you intend to have grayscaled drawings instead of coloured drawings? Could you explain?
Could you upload a typical page or pages of your drawing file for checking the proceeding? Your information is a bit slim, or should I write skinny (are these expressions possible and acceptable for usage of English?).
Good luck and success
PS
Sorry for my poor english...
Be proud of your knowledge, I could understand you pretty well!