Thanks for the hints.
I tried with the PDFJet.jar available to download in the link that you pointed, but didn't works either.
The errors are: 
Waiting for debugger to connect...
Program started.
InsertMaps (first query out of 1): INSERT INTO [InvoiceNo] ([InvNo]) VALUES (?)
InsertMaps (first query out of 1): INSERT INTO [Stock] ([AId], [Item], [Cost]) VALUES (?, ?, ?)
ExecuteMemoryTable: SELECT * FROM Stock ORDER BY [Item]
InsertMaps (first query out of 1): INSERT INTO [Acnt] ([MId], [Name], [Phone], [Address]) VALUES (?, ?, ?, ?)
InsertMaps (first query out of 1): INSERT INTO [Sales] ([SId], [MId], [Date], [Items], [Cost], [Quantity], [Total]) VALUES (?, ?, ?, ?, ?, ?, ?)
UpdateRecord: UPDATE [InvoiceNo] SET [InvNo] = ? WHERE [InvNo] = ?
java.lang.NoSuchMethodError: com.pdfjet.Font.setSize(F)V
    at uk.co.martinpearman.b4j.pdfjet.FontWrapper.SetSize(FontWrapper.java:98)
    at b4j.example.account._setpageparams(account.java:547)
    at b4j.example.account._createpdftable(account.java:500)
    at b4j.example.account._invoicebtn_action(account.java:1196)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at anywheresoftware.b4a.shell.Shell.runMethod(Shell.java:613)
    at anywheresoftware.b4a.shell.Shell.raiseEventImpl(Shell.java:231)
    at anywheresoftware.b4a.shell.Shell.raiseEvent(Shell.java:159)
    at sun.reflect.GeneratedMethodAccessor2.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at anywheresoftware.b4a.BA.raiseEvent2(BA.java:90)
    at anywheresoftware.b4a.ShellBA.raiseEvent2(ShellBA.java:93)
    at anywheresoftware.b4a.BA$1.run(BA.java:215)
    at com.sun.javafx.application.PlatformImpl.lambda$null$172(PlatformImpl.java:295)
    at java.security.AccessController.doPrivileged(Native Method)
    at com.sun.javafx.application.PlatformImpl.lambda$runLater$173(PlatformImpl.java:294)
    at com.sun.glass.ui.InvokeLaterDispatcher$Future.run(InvokeLaterDispatcher.java:95)
    at com.sun.glass.ui.win.WinApplication._enterNestedEventLoopImpl(Native Method)
    at com.sun.glass.ui.win.WinApplication._enterNestedEventLoop(WinApplication.java:204)
    at com.sun.glass.ui.Application.enterNestedEventLoop(Application.java:511)
    at com.sun.glass.ui.EventLoop.enter(EventLoop.java:107)
    at com.sun.javafx.tk.quantum.QuantumToolkit.enterNestedEventLoop(QuantumToolkit.java:583)
    at javafx.stage.Stage.showAndWait(Stage.java:474)
    at anywheresoftware.b4j.objects.Form.ShowAndWait(Form.java:215)
    at b4j.example.account._show(account.java:122)
    at b4j.example.main._inputbtn_action(main.java:136)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at anywheresoftware.b4a.shell.Shell.runMethod(Shell.java:613)
    at anywheresoftware.b4a.shell.Shell.raiseEventImpl(Shell.java:231)
    at anywheresoftware.b4a.shell.Shell.raiseEvent(Shell.java:159)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at anywheresoftware.b4a.BA.raiseEvent2(BA.java:90)
    at anywheresoftware.b4a.ShellBA.raiseEvent2(ShellBA.java:93)
    at anywheresoftware.b4a.BA$1.run(BA.java:215)
    at com.sun.javafx.application.PlatformImpl.lambda$null$172(PlatformImpl.java:295)
    at java.security.AccessController.doPrivileged(Native Method)
    at com.sun.javafx.application.PlatformImpl.lambda$runLater$173(PlatformImpl.java:294)
    at com.sun.glass.ui.InvokeLaterDispatcher$Future.run(InvokeLaterDispatcher.java:95)
    at com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
    at com.sun.glass.ui.win.WinApplication.lambda$null$147(WinApplication.java:177)
    at java.lang.Thread.run(Thread.java:748)
java.lang.RuntimeException: java.lang.NoSuchMethodError: com.pdfjet.Font.setSize(F)V
    at anywheresoftware.b4a.BA.raiseEvent2(BA.java:119)
    at anywheresoftware.b4a.ShellBA.raiseEvent2(ShellBA.java:93)
    at anywheresoftware.b4a.BA$1.run(BA.java:215)
    at com.sun.javafx.application.PlatformImpl.lambda$null$172(PlatformImpl.java:295)
    at java.security.AccessController.doPrivileged(Native Method)
    at com.sun.javafx.application.PlatformImpl.lambda$runLater$173(PlatformImpl.java:294)
    at com.sun.glass.ui.InvokeLaterDispatcher$Future.run(InvokeLaterDispatcher.java:95)
    at com.sun.glass.ui.win.WinApplication._enterNestedEventLoopImpl(Native Method)
    at com.sun.glass.ui.win.WinApplication._enterNestedEventLoop(WinApplication.java:204)
    at com.sun.glass.ui.Application.enterNestedEventLoop(Application.java:511)
    at com.sun.glass.ui.EventLoop.enter(EventLoop.java:107)
    at com.sun.javafx.tk.quantum.QuantumToolkit.enterNestedEventLoop(QuantumToolkit.java:583)
    at javafx.stage.Stage.showAndWait(Stage.java:474)
    at anywheresoftware.b4j.objects.Form.ShowAndWait(Form.java:215)
    at b4j.example.account._show(account.java:122)
    at b4j.example.main._inputbtn_action(main.java:136)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at anywheresoftware.b4a.shell.Shell.runMethod(Shell.java:613)
    at anywheresoftware.b4a.shell.Shell.raiseEventImpl(Shell.java:231)
    at anywheresoftware.b4a.shell.Shell.raiseEvent(Shell.java:159)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at anywheresoftware.b4a.BA.raiseEvent2(BA.java:90)
    at anywheresoftware.b4a.ShellBA.raiseEvent2(ShellBA.java:93)
    at anywheresoftware.b4a.BA$1.run(BA.java:215)
    at com.sun.javafx.application.PlatformImpl.lambda$null$172(PlatformImpl.java:295)
    at java.security.AccessController.doPrivileged(Native Method)
    at com.sun.javafx.application.PlatformImpl.lambda$runLater$173(PlatformImpl.java:294)
    at com.sun.glass.ui.InvokeLaterDispatcher$Future.run(InvokeLaterDispatcher.java:95)
    at com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
    at com.sun.glass.ui.win.WinApplication.lambda$null$147(WinApplication.java:177)
    at java.lang.Thread.run(Thread.java:748)
Caused by: java.lang.NoSuchMethodError: com.pdfjet.Font.setSize(F)V
    at uk.co.martinpearman.b4j.pdfjet.FontWrapper.SetSize(FontWrapper.java:98)
    at b4j.example.account._setpageparams(account.java:547)
    at b4j.example.account._createpdftable(account.java:500)
    at b4j.example.account._invoicebtn_action(account.java:1196)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at anywheresoftware.b4a.shell.Shell.runMethod(Shell.java:613)
    at anywheresoftware.b4a.shell.Shell.raiseEventImpl(Shell.java:231)
    at anywheresoftware.b4a.shell.Shell.raiseEvent(Shell.java:159)
    at sun.reflect.GeneratedMethodAccessor2.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at anywheresoftware.b4a.BA.raiseEvent2(BA.java:90)
    ... 36 more