SQL & PL/SQL

Hi,
I am having PDF files stored in BLOB column of a table in Oracle Database (11G R2).
I want to retrieve the files back and store them in hard disk. I am successful in storing the content as a file with '.doc' but if I store the file as '.pdf', adobe fails to open the file with error
Adobe Reader could not open file 'xxx.pdf' because it is either not a supported file type or because the file has been damaged (for example it was sent as an email attachment and wasn't correctly decoded)

I am using following example code to achieve my goal...

Declare
b blob;
c clob;
buffer VARCHAR2(32767);
buffer_size CONSTANT BINARY_INTEGER := 32767;
amount BINARY_INTEGER;
offset NUMBER(38);
file_handle UTL_FILE.FILE_TYPE;
begin
select blob_data into b from blobdata where id=1;
c := blob2clob(b);
file_handle := UTL_FILE.FOPEN('BLOB2FILE','my_file.pdf','w',buffer_size);
amount := buffer_size;
offset := 1;
WHILE amount >= buffer_size
LOOP
DBMS_LOB.READ(c,amount,offset,buffer);
-- buffer:=replace(buffer,chr(13),'');
offset := offset + amount;
UTL_FILE.PUT(file_handle,buffer);
UTL_FILE.FFLUSH(file_handle);
END LOOP;
UTL_FILE.FCLOSE(file_handle);
end;

create or replace FUNCTION BLOB2CLOB ( p_blob IN BLOB ) RETURN CLOB
-- typecasts BLOB to CLOB (binary conversion)
IS
/*****************************************************************************************
|| Purpose : To Convert a BLOB File to CLOB File
|| INPUT : BLOB File
|| OUTPUT : CLOB File
|| History: MB V5.0 24.09.2007 RCMS00318572 Initial version
*****************************************************************************************/
ln_file_check NUMBER;
ln_file_size NUMBER;
v_text_file CLOB;
v_binary_file BLOB;
v_dest_offset INTEGER := 1;
v_src_offset INTEGER := 1;
v_warning INTEGER;
lv_data CLOB;
ln_length NUMBER;
csid VARCHAR2(100) := DBMS_LOB.DEFAULT_CSID;
V_LANG_CONTEXT NUMBER := DBMS_LOB.DEFAULT_LANG_CTX;
BEGIN
DBMS_LOB.createtemporary (v_text_file, TRUE);
SELECT dbms_lob.getlength(p_blob) INTO ln_file_size FROM DUAL;
DBMS_LOB.converttoclob (v_text_file, p_blob, ln_file_size, v_dest_offset, v_src_offset, 0, v_lang_context, v_warning);
SELECT dbms_lob.getlength(v_text_file) INTO ln_length FROM DUAL;
RETURN v_text_file;
END;