You can change the font sizes by editing %appdata%\LDCad\gui\default\main.gui
But it doesn't work great for all text's yet, I'll try to improve this for the 1.6 version.
I've played around a bit and below seems a working configuration (making most things 1.5 - 2 times bigger). Just replace the fonts section in main.gui with it.
Code:
startMenu_cap=DejaVuSans,FreeSans,verdana,64
startMenu_recentCap=DejaVuSans,FreeSans,verdana,40
startMenu_recentItem=DejaVuSans,FreeSans,verdana,36
menu_capS1=DejaVuSans,FreeSans,verdana,40
menu_capS2=DejaVuSans,FreeSans,verdana,32
menu_itemS1=DejaVuSans,FreeSans,verdana,32
menu_itemS2=DejaVuSans,FreeSans,verdana,24
menu_sepCapS1=DejaVuSans,FreeSans,verdana,24
menu_sepCapS2=DejaVuSans,FreeSans,verdana,20
menuBar_item=DejaVuSans,FreeSans,verdana,22
bin_viewNr=DejaVuSans,FreeSans,verdana,36
bin_viewCap=DejaVuSans,FreeSans,verdana,20
colorBin_menuItemCap=DejaVuSans,FreeSans,verdana,20
colorBin_pageInfo=DejaVuSans,FreeSans,verdana,20
partBin_search=DejaVuSans,FreeSans,verdana,20
partBin_syncMsg=DejaVuSans,FreeSans,verdana,32
partBin_partCntS1=DejaVuSans,FreeSans,verdana,20
partBin_partCntS2=DejaVuSans,FreeSans,verdana,24
guiLabel_defCap=DejaVuSans,FreeSans,verdana,36
guiLabel_insNestSFCap=DejaVuSans,FreeSans,verdana,28
editSesPanel_tabCap=DejaVuSans,FreeSans,verdana,28
editSesPanel_opt=DejaVuSans,FreeSans,verdana,28
editSesPanel_cur=DejaVuSans,FreeSans,verdana,28
compass_text=DejaVuSans,FreeSans,verdana,36
angleInfoPanel_text=DejaVuSans,FreeSans,verdana,36
selInfoPanel_text=DejaVuSans,FreeSans,verdana,36
partInfoPanel_textS1=DejaVuSansMono,FreeMono,cour,FreeSans,36
partInfoPanel_textS2=DejaVuSansMono,FreeMono,cour,FreeSans,28
partInfoPanel_textS3=DejaVuSansMono,FreeMono,cour,FreeSans,20
docInfoPanel_cap=DejaVuSans,FreeSans,verdana,36
docInfoPanel_text=DejaVuSans,FreeSans,verdana,28
animationPanel_pos=DejaVuSans,FreeSans,verdana,36
sourceWin_text=DejaVuSansMono,FreeMono,cour,FreeSans,24